Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760469AbZCPXYT (ORCPT ); Mon, 16 Mar 2009 19:24:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752165AbZCPXYD (ORCPT ); Mon, 16 Mar 2009 19:24:03 -0400 Received: from smtp-out.google.com ([216.239.33.17]:63045 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847AbZCPXX6 (ORCPT ); Mon, 16 Mar 2009 19:23:58 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding:x-system-of-record; b=F/x98lyPPWfoCuG4pkBMMo8zveHNV1dDCkAFWFqvBkaOy25jJKrRfUXk0/gT8CqVE pVE2r+AdcA0sBQbZkYTbg== MIME-Version: 1.0 In-Reply-To: <20090313170415.GE3354@Krystal> References: <5df78e1d0902231610y615bcfb5hdbbc44736ecfce00@mail.gmail.com> <20090313170415.GE3354@Krystal> Date: Mon, 16 Mar 2009 16:23:48 -0700 Message-ID: <5df78e1d0903161623s1d5d2a04h946668ac0c6a69f7@mail.gmail.com> Subject: Re: [RFC PATCH] Propose a new kernel tracing framework From: Jiaying Zhang To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, Steven Rostedt , Michael Rubin , Martin Bligh , Michael Davidson , ltt-dev@lists.casi.polymtl.ca, Ingo Molnar Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 51220 Lines: 1302 Hi Mathieu, First, I apologize that I did not forward you my original email. I assumed that the email would be noticed by interested people when it was sent to lkml. Now I see that is a mistake. On Fri, Mar 13, 2009 at 10:04 AM, Mathieu Desnoyers wrote: > Hi Jiaying, > > I'm very interested to hear about the details of your test-case, because > what you are talking about here, and the numbers that you get, are, at > the very least, not representative of the current LTTng. Perharps you > used a version right after the kernel summit and stopped following the > improvements we have done since then ? I also wonder about the instrumentation > set you enabled in your tests, and whether it's exactly the same in the ktrace > and LTTng runs (especially system call tracing). Please note that following the > Kernel Summit 2008, a more active development cycle began, and the time was not > right for optimisation. But since then a lot of improvement has been done on > this side. Sorry that I omitted a lot of details in my test description. I did use an old version of LTTng in my tests. The LTTng version I used was the 0.21 lttng patches for 2.6.27 kernel. I used 2.6.26 kernel in my tests, with the ported lttng-2.6.27-rc6-0.21 patches. I enabled the same set of trace events in ktrace and LTTng runs. Here is the list of enabled events: syscall entry/exit, irq entry/exit, trap entry/exit, kernel_sched_switch, kernel_process_fork, kernel_process_wait, kernel_process_free, kernel_process_exit. We are glad to see the improvements coming from the LTTng community. I haven't got time to sync with the latest LTTng code and re-run my tests. I will let you know when I have such data available. > > First I'd like to express my concern about the way you posted your > numbers : > > 1 - You did not CC anyone from the LTTng project. > 2 - You did not tell which LTTng version you used as a comparison basis. > 3 - You did not look at the current state of code before posting your > comparison. (as shows the comment in your patch header) That is indeed my mistake. > 4 - You did not tell the instrumentation set that you enabled from LTTng. Is it > the default instrumentation ? Did you also enable system call tracing > with your tracer using set_kernel_trace_flag_all_tasks() ? If not, this > makes a huge difference on the amount of information gathered. Yes. We also enable syscall tracing via set_kernel_trace_flag_all_tasks(). > > So let's have a close look at them. I'm re-doing the benchmarks based on > the current LTTng version below. > >> Hello All, >> >> We have been working on building a kernel tracer for a production environment. >> We first considered to use the existing markers code, but found it a bit >> heavyweight. > > Have you looked at : > > 1 - The tracepoints currently in the kernel > 2 - The _current_ version of markers in the LTTng tree ? I looked at the tracepoints currently in the kernel. It is great to see that some trace instrumentation code is finally available in the mainline kernel. But I still don't like an additional tracepoint layer on top of the actual tracing (ktrace or markers or ftrace) layer. That seems to add unnecessary overhead. The markers code I referred to in my email is the current code in the mainline kernel. I had a look at the LTTng markers code but still saw that va_list argument is used in marker_probe_func. It sounds a nice improvement if the LTTng markers avoids the use of va_arg whenever possible. > >> So we developed a new kernel tracing prototype that shares >> many similarities as markers but also includes several simplifications that >> give us considerable performance benefits. For example, we pass the size of >> trace event directly to the probe function instead of using va_arg as that >> used in markers, which saves us the overhead of variable passing. > > The markers in the LTTng tree only use va_args for "debug-style" > tracing. All the tracing fast paths are now done with custom probe > functions which takes the arguments from the tracepoint and write them > in the trace buffers directly in C. When the event payload size is already > known statically, there is no dynamic computation cost at all : it's > simply passed to the ltt-relay write function. But this raises another concern that sub-system developers may need to write a bunch of custom probe functions to avoid the argument parsing overhead. Can you instead have a general probe function or macro that does this work? > >> Also, we >> associate a single probe function to each event, so we can directly call the >> probe function when tracing is enabled. > > You seem to imply that being stuck with a single probe function is > somehow superior to have tiny per-event callbacks which then call into a > buffer write function ? Why ? That is indeed my thinking, because we saw that some platforms are very sensitive to function call overhead and we haven't seen use cases where multi probe functions prove necessary. > >> Our measurements show that our >> current tracing prototype introduces much lower overhead compared with >> lttng (we use lttng as a comparison because markers does not provide the >> implementation to record trace data). > > Why LTTng version, kernel version, LTTng config and runtime options do > you use ? See above for LTTng and kernel versions. I was using the default LTTng config options and 'normal' recorder mode. > >> E.g., with dbench, lttng introduces >> 20~80% overhead on our testing platforms while the overhead with our >> kernel tracer is within 10%; with tbench, lttng usually adds more than 30% >> overhead while the overhead added by our kernel tracer is usually within >> 15%; with kernbench (time to compile a Linux kernel), the overhead >> added by lttng is around 4%~18% while the overhead added by our >> kernel tracer is within 2.5%. >> > > I'm re-running the dbench and tbench tests : > > With LTTng 0.106, kernel 2.6.29-rc7 > 8-cores Intel(R) Xeon(R) CPU E5405 @ 2.00GHz, 16GB ram > > Arming all the default LTTng instrumentation (168 tracepoints), > Tracing in flight recorder mode, including system call entry/exit > tracing and block I/O tracing (blktrace instrumentation), I get : > > Test / config | Vanilla kernel | LTTng 0.106 | slowdown > dbench 8 -t 200 | 1361 MB/s | 1193 MB/s | 12.3 % > > As an example of the effect of custom probe vs va_args based probes, > let's take the tbench example > > | Vanilla | LTTng 0.106 | slowdown > tbench 8 -t 200 | 2074 MB/s | 997 MB/s | 52 % > > The LTTng trace statistics shows the top high event rate events : > > Some are usual (therefore lttng already implements custom probes for them) : > > 42004 sched_try_wakeup > 79754 timer_set > 83973 sched_schedule > 84317 softirq_exit > 84318 softirq_entry > 95370 page_free > 95412 page_alloc > 267247 syscall_entry > 267247 syscall_exit > > Some are more tbench workload-specific : > > 16915 socket_sendmsg > 18911 napi_complete > 18911 napi_schedule > 18912 dev_receive > 18914 dev_xmit > 18920 napi_poll > 33831 socket_recvmsg > 59860 read > > > So let's see what happens if I implement those as custom probes and do a bit of > tuning in the tracer hot path : Could you give more details about the custom probe you used? Do you need to write a custom probe for each tracepoint? Jiaying > > | Vanilla | LTTng 0.107 | slowdown > Custom probes : > tbench 8 -t 200 | 2074 MB/s | 1275 MB/s | 38.5 % > > With tracer hot path tuning (inline hot path, function calls for slow path, will > be in 0.108) : > tbench 8 -t 200 | 2074 MB/s | 1335 MB/s | 35.6 % > > kernbench : > Average Optimal load -j 32 Run > > Vanilla 2.6.29-rc7 : > Elapsed Time 48.238 (0.117346) > > With flight recorder tracing, default lttng instrumentation, lttng 0.108 : > Elapsed Time 50.226 (0.0750333) > > Slowdown : 4.1 % > > So except the tbench workload on LTTng 0.106, which still had a 52% performance > impact (brought it down to 35 % for the next LTTng release) due to > specific workload and not having specialized probes implemented, the > dbench impact is well below your results (12.3 % vs 20-80%) > > So given the huge result discrepancies between your tests and mine, could you > give us more detail about your benchmarks ? Especially knowing the enabled > instrumentation set, and the amount of MB/s generated by both ktrace and LTTng > runs (to make sure we are comparing the same traffic) and the LTTng versions you > are using as a comparison basis would be good. > > Thanks, > > Mathieu > > >> The patch below is the current prototype we have implemented. It uses >> Steve's unified trace buffer code with some small extensions to support >> buffer mmap. The patch is probably still buggy, but we would like to get >> some early feedback from the community. >> >> Signed-off-by: Jiaying Zhang >> >> Index: git-linux/init/Kconfig >> =================================================================== >> --- git-linux.orig/init/Kconfig 2009-02-19 14:58:37.000000000 -0800 >> +++ git-linux/init/Kconfig 2009-02-19 15:50:15.000000000 -0800 >> @@ -950,6 +950,15 @@ >> Place an empty function call at each marker site. Can be >> dynamically changed for a probe function. >> >> +config KTRACE >> + bool "Enable ktrace support" >> + select DEBUG_FS >> + select TRACING >> + select RING_BUFFER >> + help >> + Ktrace is a kernel tracing tool that allows you to trace >> + kernel events by inserting trace points at proper places. >> + >> source "arch/Kconfig" >> >> endmenu # General setup >> Index: git-linux/kernel/Makefile >> =================================================================== >> --- git-linux.orig/kernel/Makefile 2009-02-19 14:58:37.000000000 -0800 >> +++ git-linux/kernel/Makefile 2009-02-19 14:58:39.000000000 -0800 >> @@ -86,6 +86,7 @@ >> obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o >> obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o >> obj-$(CONFIG_MARKERS) += marker.o >> +obj-$(CONFIG_KTRACE) += ktrace.o >> obj-$(CONFIG_TRACEPOINTS) += tracepoint.o >> obj-$(CONFIG_LATENCYTOP) += latencytop.o >> obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o >> Index: git-linux/include/asm-generic/vmlinux.lds.h >> =================================================================== >> --- git-linux.orig/include/asm-generic/vmlinux.lds.h 2009-02-19 >> 14:58:37.000000000 -0800 >> +++ git-linux/include/asm-generic/vmlinux.lds.h 2009-02-19 >> 14:58:39.000000000 -0800 >> @@ -73,6 +73,9 @@ >> MEM_KEEP(init.data) \ >> MEM_KEEP(exit.data) \ >> . = ALIGN(8); \ >> + VMLINUX_SYMBOL(__start___ktraces) = .; \ >> + *(__ktrace) \ >> + VMLINUX_SYMBOL(__stop___ktraces) = .; \ >> VMLINUX_SYMBOL(__start___markers) = .; \ >> *(__markers) \ >> VMLINUX_SYMBOL(__stop___markers) = .; \ >> @@ -89,6 +92,7 @@ >> VMLINUX_SYMBOL(__start_rodata) = .; \ >> *(.rodata) *(.rodata.*) \ >> *(__vermagic) /* Kernel version magic */ \ >> + *(__ktrace_strings) /* Ktrace: strings */ \ >> *(__markers_strings) /* Markers: strings */ \ >> *(__tracepoints_strings)/* Tracepoints: strings */ \ >> } \ >> Index: git-linux/kernel/module.c >> =================================================================== >> --- git-linux.orig/kernel/module.c 2009-02-19 14:58:37.000000000 -0800 >> +++ git-linux/kernel/module.c 2009-02-19 14:58:39.000000000 -0800 >> @@ -50,6 +50,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> #if 0 >> @@ -2145,6 +2146,10 @@ >> sizeof(*mod->tracepoints), >> &mod->num_tracepoints); >> #endif >> +#ifdef CONFIG_KTRACE >> + mod->ktrace = section_objs(hdr, sechdrs, secstrings, "__ktrace", >> + sizeof(*mod->ktrace), &mod->num_ktrace); >> +#endif >> >> #ifdef CONFIG_MODVERSIONS >> if ((mod->num_syms && !mod->crcs) >> Index: git-linux/include/linux/module.h >> =================================================================== >> --- git-linux.orig/include/linux/module.h 2009-02-19 >> 14:58:37.000000000 -0800 >> +++ git-linux/include/linux/module.h 2009-02-19 14:58:39.000000000 -0800 >> @@ -44,6 +44,7 @@ >> }; >> >> struct module; >> +struct kernel_trace; >> >> struct module_attribute { >> struct attribute attr; >> @@ -347,6 +348,11 @@ >> /* Reference counts */ >> struct module_ref ref[NR_CPUS]; >> #endif >> +#ifdef CONFIG_KTRACE >> + struct kernel_trace *ktrace; >> + unsigned int num_ktrace; >> +#endif >> + >> }; >> #ifndef MODULE_ARCH_INIT >> #define MODULE_ARCH_INIT {} >> Index: git-linux/include/linux/ktrace.h >> =================================================================== >> --- /dev/null 1970-01-01 00:00:00.000000000 +0000 >> +++ git-linux/include/linux/ktrace.h 2009-02-19 15:36:39.000000000 -0800 >> @@ -0,0 +1,83 @@ >> +#ifndef _LINUX_KTRACE_H >> +#define _LINUX_KTRACE_H >> + >> +#include >> + >> +struct kernel_trace; >> + >> +typedef void ktrace_probe_func(struct kernel_trace *, void *, size_t); >> + >> +struct kernel_trace { >> + const char *name; >> + const char *format; /* format string describing variable list */ >> + size_t *stroff; /* offsets of string variables */ >> + /* 31 bit event_id is converted to 16 bit when entering to the buffer */ >> + u32 enabled:1, event_id:31; >> + ktrace_probe_func *func; /* probe function */ >> + struct list_head list; /* list head linked to the hash table entry */ >> +} __attribute__((aligned(8))); >> + >> +extern int ktrace_enabled; >> + >> +/* >> + * Make sure the alignment of the structure in the __ktrace section will >> + * not add unwanted padding between the beginning of the section and the >> + * structure. Force alignment to the same alignment as the section start. >> + */ >> + >> +#define DEFINE_KTRACE_STRUCT(name) \ >> + struct __attribute__((packed)) ktrace_struct_##name >> + >> +#ifdef CONFIG_KTRACE >> +/* >> + * DO_TRACE is the macro that is called from each trace point. Each trace >> + * point is associated with a static ktrace object that is located in a >> + * special __ktrace section and is uniquely identified by the event name and >> + * event format. Take a look at the files under include/trace for example >> + * usage. Note that we call the trace probe function only if the global >> + * tracing is enabled and the tracing for the associated event is enabled, >> + * so we only introduce the overhead of a predicted condition judge when >> + * tracing is disabled. >> + */ >> +#define DO_TRACE(name, format, args...) >> \ >> + do { \ >> + static const char __kstrtab_##name[] \ >> + __attribute__((section("__ktrace_strings"))) \ >> + = #name "\0" format; \ >> + static struct kernel_trace __ktrace_##name \ >> + __attribute__((section("__ktrace"), aligned(8))) = \ >> + { __kstrtab_##name, &__kstrtab_##name[sizeof(#name)], \ >> + NULL, 0, 0, NULL, LIST_HEAD_INIT(__ktrace_##name.list) }; \ >> + __ktrace_check_format(format, ## args); \ >> + if (unlikely(ktrace_enabled) && \ >> + unlikely(__ktrace_##name.enabled)) { \ >> + struct ktrace_struct_##name karg = { args }; \ >> + (*__ktrace_##name.func) \ >> + (&__ktrace_##name, &karg, sizeof(karg)); \ >> + } \ >> + } while (0) >> + >> +#else /* !CONFIG_KTRACE */ >> +#define DO_TRACE(name, format, args...) >> +#endif >> + >> +/* To be used for string format validity checking with gcc */ >> +static inline void __printf(1, 2) ___ktrace_check_format(const char *fmt, ...) >> +{ >> +} >> + >> +#define __ktrace_check_format(format, args...) \ >> + do { \ >> + if (0) \ >> + ___ktrace_check_format(format, ## args); \ >> + } while (0) >> + >> + >> +/* get the trace buffer information */ >> +#define KTRACE_BUF_GET_SIZE _IOR(0xF5, 0x00, __u32) >> +#define KTRACE_BUF_GET_PRODUCED _IOR(0xF5, 0x01, __u32) >> +#define KTRACE_BUF_GET_CONSUMED _IOR(0xF5, 0x02, __u32) >> +#define KTRACE_BUF_PUT_PRODUCED _IOW(0xF5, 0x03, __u32) >> +#define KTRACE_BUF_PUT_CONSUMED _IOW(0xF5, 0x04, __u32) >> + >> +#endif >> Index: git-linux/kernel/ktrace.c >> =================================================================== >> --- /dev/null 1970-01-01 00:00:00.000000000 +0000 >> +++ git-linux/kernel/ktrace.c 2009-02-19 15:45:20.000000000 -0800 >> @@ -0,0 +1,872 @@ >> +/* >> + * kernel/ktrace.c >> + * >> + * Implementation of the kernel tracing for linux kernel 2.6. >> + * >> + * Copyright 2008- Google Inc. >> + * Original Author: Jiaying Zhang >> + */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +static char *ktrace_version = "1.0.0"; >> +int ktrace_enabled; >> +EXPORT_SYMBOL(ktrace_enabled); >> +static uint16_t ktrace_next_id; >> + >> +extern struct kernel_trace __start___ktraces[]; >> +extern struct kernel_trace __stop___ktraces[]; >> + >> +static DEFINE_MUTEX(ktrace_mutex); >> + >> +/* ktrace hash table entry structure and variables */ >> +struct ktrace_entry { >> + struct hlist_node hlist; >> + char *name; >> + char *format; >> + size_t *stroff; >> + ktrace_probe_func *func; >> + u32 enabled:1, event_id:31; >> + struct list_head klist; /* list of loaded ktraces */ >> +}; >> + >> +#define KTRACE_HASH_BITS 6 >> +#define KTRACE_HASH_SIZE (1 << KTRACE_HASH_BITS) >> +static struct hlist_head ktrace_table[KTRACE_HASH_SIZE]; >> + >> +/* debugfs directory variables */ >> +static struct dentry *tracedir; >> +static struct dentry *eventdir; >> +typedef void tracecontrol_handle_func(struct file *, unsigned long, size_t *); >> + >> +/* ring buffer code */ >> +static unsigned long trace_buf_size = 65536UL; >> +struct ring_buffer *trace_buffer; >> +static DECLARE_WAIT_QUEUE_HEAD(trace_wait); /* waitqueue for trace_data_poll */ >> +static struct timer_list trace_timer; /* reader wake-up timer */ >> +#define TRACEREAD_WAKEUP_INTERVAL 1000 /* time interval in jiffies */ >> +static struct kref ktrace_kref; >> + >> +static void >> +ring_buffer_probe(struct kernel_trace *kt, void *data, size_t event_size) >> +{ >> + struct ring_buffer_event *event; >> + void *trace_event; >> + unsigned long flag; >> + >> + event = ring_buffer_lock_reserve(trace_buffer, >> + sizeof(uint16_t) + event_size, &flag); >> + if (!event) >> + return; >> + trace_event = ring_buffer_event_data(event); >> + *(uint16_t *) trace_event = (uint16_t) kt->event_id; >> + memcpy(trace_event + sizeof(uint16_t), data, event_size); >> + ring_buffer_unlock_commit(trace_buffer, event, flag); >> +} >> + >> +/* special probe function for events that contain string arguments */ >> +static void >> +string_probe(struct kernel_trace *kt, void *data, size_t event_size) >> +{ >> + struct ring_buffer_event *event; >> + void *trace_event, *p; >> + unsigned long flag; >> + size_t *offset, scanned; >> + char *string; >> + >> + /* >> + * Get the real length of the event, i.e., we use stroff array to >> + * locate string variables in the passed-in trace data and use their >> + * length to replace the size of the string pointers. >> + */ >> + for (offset = kt->stroff; *offset != -1; offset++) { >> + string = *(char **) (data + *offset); >> + event_size += strlen(string) + 1 - sizeof(char *); >> + } >> + event = ring_buffer_lock_reserve(trace_buffer, >> + sizeof(uint16_t) + event_size, &flag); >> + if (!event) >> + return; >> + trace_event = ring_buffer_event_data(event); >> + *(uint16_t *) trace_event = (uint16_t) kt->event_id; >> + p = trace_event + sizeof(uint16_t); >> + /* >> + * Copy the trace data into buffer. For string variables, we enter the >> + * string into the buffer. Otherwise, the passed in data is copied. >> + */ >> + for (offset = kt->stroff, scanned = 0; *offset != -1; offset++) { >> + memcpy(p, data + scanned, *offset - scanned); >> + p += *offset - scanned; >> + string = *(char **) (data + *offset); >> + memcpy(p, string, strlen(string) + 1); >> + p += strlen(string) + 1; >> + scanned = *offset + sizeof(char *); >> + } >> + memcpy(p, data + scanned, >> + trace_event + sizeof(uint16_t) + event_size - p); >> + ring_buffer_unlock_commit(trace_buffer, event, flag); >> +} >> + >> +/* timer function used to defer ring buffer reader waking */ >> +static void wakeup_readers(unsigned long data) >> +{ >> + if (trace_buffer && !ring_buffer_empty(trace_buffer)) >> + wake_up_interruptible(&trace_wait); >> + mod_timer(&trace_timer, jiffies + TRACEREAD_WAKEUP_INTERVAL); >> +} >> + >> +/* function for reading ktrace metadata info */ >> +static void *tracing_info_start(struct seq_file *seq, loff_t *pos) >> +{ >> + seq_printf(seq, "version %s\n", ktrace_version); >> + return (*pos >= KTRACE_HASH_SIZE) ? NULL : &ktrace_table[*pos]; >> +} >> + >> +static void *tracing_info_next(struct seq_file *seq, void *v, loff_t *pos) >> +{ >> + ++*pos; >> + return (*pos >= KTRACE_HASH_SIZE) ? NULL : &ktrace_table[*pos]; >> +} >> + >> +static int tracing_info_show(struct seq_file *seq, void *v) >> +{ >> + struct hlist_head *head = v; >> + struct hlist_node *node; >> + struct ktrace_entry *entry; >> + hlist_for_each_entry(entry, node, head, hlist) >> + seq_printf(seq, "name '%s' format '%s' id %u %s\n", >> + entry->name, entry->format, entry->event_id, >> + entry->enabled ? "enabled" : "disabled"); >> + return 0; >> +} >> + >> +static void tracing_info_stop(struct seq_file *seq, void *v) >> +{ >> +} >> + >> +static const struct seq_operations tracing_info_seq_ops = { >> + .start = tracing_info_start, >> + .next = tracing_info_next, >> + .show = tracing_info_show, >> + .stop = tracing_info_stop, >> +}; >> + >> +static int tracing_info_open(struct inode *inode, struct file *file) >> +{ >> + return seq_open(file, &tracing_info_seq_ops); >> +} >> + >> +static const struct file_operations traceinfo_file_operations = { >> + .open = tracing_info_open, >> + .read = seq_read, >> + .llseek = seq_lseek, >> + .release = seq_release, >> +}; >> + >> +/* >> + * wrapper function used by debugfs write operation. >> + * func: handling function that does real work >> + */ >> +static ssize_t trace_debugfs_write(struct file *filp, const char __user *ubuf, >> + size_t cnt, loff_t *ppos, tracecontrol_handle_func *func) >> +{ >> + int ret; >> + char buf[64]; >> + unsigned long val; >> + >> + if (cnt >= sizeof(buf)) >> + return -EINVAL; >> + if (copy_from_user(&buf, ubuf, cnt)) >> + return -EFAULT; >> + buf[cnt] = 0; >> + >> + ret = strict_strtoul(buf, 10, &val); >> + if (ret < 0) >> + return ret; >> + val = !!val; >> + >> + func(filp, val, &cnt); >> + >> + filp->f_pos += cnt; >> + return cnt; >> +} >> + >> +/* functions for reading/writing the global 'enabled' control file */ >> +static ssize_t tracing_control_read(struct file *filp, char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + int ret; >> + char buf[64]; >> + ret = snprintf(buf, 64, "%u\n", ktrace_enabled); >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, ret); >> +} >> + >> +static void __tracing_control_write(struct file *filp, >> + unsigned long val, size_t *cnt) >> +{ >> + if (val ^ ktrace_enabled) { >> + if (val) { >> + trace_timer.expires = >> + jiffies + TRACEREAD_WAKEUP_INTERVAL; >> + add_timer(&trace_timer); >> + ktrace_enabled = 1; >> + } else { >> + ktrace_enabled = 0; >> + del_timer_sync(&trace_timer); >> + if (trace_buffer && !ring_buffer_empty(trace_buffer)) >> + wake_up_interruptible(&trace_wait); >> + } >> + } >> +} >> + >> +static ssize_t tracing_control_write(struct file *filp, const char >> __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + return trace_debugfs_write(filp, ubuf, cnt, ppos, >> + __tracing_control_write); >> +} >> + >> +static const struct file_operations tracecontrol_file_operations = { >> + .read = tracing_control_read, >> + .write = tracing_control_write, >> +}; >> + >> +/* functions for reading/writing a trace event file */ >> +static int update_ktrace(struct ktrace_entry *entry, >> + ktrace_probe_func *func, int enabled) >> +{ >> + struct kernel_trace *iter; >> + /* no need to update the list if the tracing is not initialized */ >> + if (!tracedir) >> + return 0; >> + entry->enabled = enabled; >> + entry->func = func; >> + list_for_each_entry(iter, &entry->klist, list) { >> + iter->stroff = entry->stroff; >> + iter->func = func; >> + iter->enabled = enabled; >> + } >> + return 0; >> +} >> + >> +static int ktrace_probe_register(struct ktrace_entry *entry, >> + ktrace_probe_func *probefunc) >> +{ >> + return update_ktrace(entry, probefunc, 1); >> +} >> + >> +static int ktrace_probe_unregister(struct ktrace_entry *entry) >> +{ >> + return update_ktrace(entry, NULL, 0); >> +} >> + >> +static int ktrace_control_open(struct inode *inode, struct file *filp) >> +{ >> + filp->private_data = inode->i_private; >> + return 0; >> +} >> + >> +static ssize_t ktrace_control_read(struct file *filp, char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + int ret; >> + char buf[64]; >> + struct ktrace_entry *entry = filp->private_data; >> + >> + ret = snprintf(buf, 64, "%u\n", entry->enabled); >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, ret); >> +} >> + >> +/* >> + * Check whether the event contains string arguments. Return 0 if not; >> + * otherwise record the offsets of the string arguments in the ktrace >> + * structure according to the event format and return 1. >> + * The offset info is later used to store the string arguments into >> + * the trace buffer during trace probe. >> + */ >> +static int contain_string_arguments(struct ktrace_entry *entry) >> +{ >> + int count = 0; >> + char *fmt; >> + int qualifier; /* 'h', 'l', or 'L' for integer fields */ >> + size_t offset = 0; >> + >> + for (fmt = strstr(entry->format, "%s"); fmt; fmt = strstr(++fmt, "%s")) >> + count++; >> + if (!count) >> + return 0; >> + entry->stroff = kmalloc(sizeof(size_t) * (count + 1), GFP_KERNEL); >> + if (!entry->stroff) >> + return -ENOMEM; >> + >> + for (fmt = entry->format, count = 0; *fmt ; ++fmt) { >> + if (*fmt != '%') >> + continue; >> +repeat: >> + ++fmt; >> + switch (*fmt) { >> + case '-': >> + case '+': >> + case ' ': >> + case '#': >> + case '0': >> + ++fmt; >> + goto repeat; >> + } >> + >> + while (isdigit(*fmt)) >> + fmt++; >> + >> + /* get the conversion qualifier */ >> + qualifier = -1; >> + if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') { >> + qualifier = *fmt; >> + ++fmt; >> + if (qualifier == 'l' && *fmt == 'l') { >> + qualifier = 'L'; >> + ++fmt; >> + } >> + } >> + >> + switch (*fmt) { >> + case 'c': >> + offset += sizeof(char); >> + continue; >> + case 's': >> + entry->stroff[count] = offset; >> + count++; >> + offset += sizeof(char *); >> + continue; >> + case 'p': >> + offset += sizeof(void *); >> + continue; >> + case 'd': >> + case 'i': >> + case 'o': >> + case 'u': >> + case 'x': >> + case 'X': >> + switch (qualifier) { >> + case 'L': >> + offset += sizeof(long long); >> + break; >> + case 'l': >> + offset += sizeof(long); >> + break; >> + case 'h': >> + offset += sizeof(short); >> + break; >> + default: >> + offset += sizeof(int); >> + break; >> + } >> + break; >> + default: >> + printk(KERN_WARNING "unknown format '%c'", *fmt); >> + continue; >> + } >> + } >> + entry->stroff[count] = -1; >> + return 1; >> +} >> + >> +static void __ktrace_control_write(struct file *filp, >> + unsigned long val, size_t *cnt) >> +{ >> + struct ktrace_entry *entry = filp->private_data; >> + int ret; >> + >> + mutex_lock(&ktrace_mutex); >> + if (val ^ entry->enabled) { >> + if (val) { >> + ret = contain_string_arguments(entry); >> + if (ret == 0) >> + ktrace_probe_register(entry, ring_buffer_probe); >> + else if (ret > 0) >> + ktrace_probe_register(entry, string_probe); >> + else >> + *cnt = ret; >> + } else >> + ktrace_probe_unregister(entry); >> + } >> + mutex_unlock(&ktrace_mutex); >> +} >> + >> +static ssize_t ktrace_control_write(struct file *filp, const char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + return trace_debugfs_write(filp, ubuf, cnt, ppos, >> + __ktrace_control_write); >> +} >> + >> +static const struct file_operations ktracecontrol_file_operations = { >> + .open = ktrace_control_open, >> + .read = ktrace_control_read, >> + .write = ktrace_control_write, >> +}; >> + >> +/* functions for adding/removing a trace event. Protected by mutex lock. >> + * Called during initialization or after loading a module */ >> +static struct ktrace_entry *add_ktrace(struct kernel_trace *ktrace) >> +{ >> + struct ktrace_entry *entry; >> + size_t name_len = strlen(ktrace->name) + 1; >> + u32 hash = jhash(ktrace->name, name_len-1, 0); >> + struct hlist_head *head; >> + struct hlist_node *node; >> + struct dentry *dentry; >> + >> + if (!tracedir) >> + return 0; >> + head = &ktrace_table[hash & ((1 << KTRACE_HASH_BITS)-1)]; >> + hlist_for_each_entry(entry, node, head, hlist) { >> + if (!strcmp(ktrace->name, entry->name)) { >> + if (strcmp(ktrace->format, entry->format)) { >> + printk(KERN_WARNING "the format of tracepoint " >> + "\'%s\' changes from \'%s\' to \'%s\'." >> + "Dynamic changing of trace format is " >> + "not supported yet!\n", >> + ktrace->name, entry->format, >> + ktrace->format); >> + return ERR_PTR(-EINVAL); >> + } >> + ktrace->enabled = entry->enabled; >> + ktrace->func = entry->func; >> + ktrace->event_id = entry->event_id; >> + if (list_empty(&entry->klist)) >> + goto add_head; >> + list_add_tail(&ktrace->list, &entry->klist); >> + return entry; >> + } >> + } >> + entry = kmalloc(sizeof(struct ktrace_entry), GFP_KERNEL); >> + if (!entry) >> + return ERR_PTR(-ENOMEM); >> + entry->name = kmalloc(name_len, GFP_KERNEL); >> + if (!entry->name) { >> + kfree(entry); >> + return ERR_PTR(-ENOMEM); >> + } >> + memcpy(entry->name, ktrace->name, name_len); >> + if (ktrace->format) { >> + size_t format_len = strlen(ktrace->format) + 1; >> + entry->format = kmalloc(format_len, GFP_KERNEL); >> + if (!entry->format) { >> + kfree(entry->name); >> + kfree(entry); >> + return ERR_PTR(-ENOMEM); >> + } >> + memcpy(entry->format, ktrace->format, format_len); >> + } else >> + entry->format = NULL; >> + entry->func = ktrace->func; >> + entry->enabled = 0; >> + ktrace->event_id = entry->event_id = ktrace_next_id++; >> + entry->stroff = NULL; >> + INIT_LIST_HEAD(&entry->klist); >> + hlist_add_head(&entry->hlist, head); >> +add_head: >> + list_add(&ktrace->list, &entry->klist); >> + dentry = debugfs_create_file(entry->name, 0660, eventdir, >> + entry, &ktracecontrol_file_operations); >> + if (!dentry) >> + printk(KERN_WARNING "Couldn't create debugfs '%s' entry\n", >> + entry->name); >> + return entry; >> +} >> + >> +static int remove_ktrace(struct kernel_trace *ktrace, int free) >> +{ >> + struct ktrace_entry *entry; >> + size_t name_len = strlen(ktrace->name) + 1; >> + u32 hash = jhash(ktrace->name, name_len-1, 0); >> + struct hlist_head *head; >> + struct hlist_node *node, *temp; >> + struct dentry *dentry; >> + >> + if (!tracedir) >> + return 0; >> + list_del(&ktrace->list); >> + head = &ktrace_table[hash & ((1 << KTRACE_HASH_BITS)-1)]; >> + hlist_for_each_entry_safe(entry, node, temp, head, hlist) >> + if (!strcmp(ktrace->name, entry->name)) { >> + if (list_empty(&entry->klist)) { >> + dentry = lookup_one_len(entry->name, >> + eventdir, strlen(entry->name)); >> + if (dentry && !IS_ERR(dentry)) { >> + debugfs_remove(dentry); >> + dput(dentry); >> + } >> + entry->enabled = 0; >> + if (free) { >> + hlist_del(&entry->hlist); >> + kfree(entry->name); >> + kfree(entry->format); >> + kfree(entry->stroff); >> + kfree(entry); >> + } >> + } >> + return 0; >> + } >> + return -1; >> +} >> + >> +/* Add/remove tracepoints contained in a module to the ktrace hash table. >> + * Called at the end of module load/unload. */ >> +static int ktrace_module_notify(struct notifier_block *self, >> + unsigned long val, void *data) >> +{ >> +#ifdef CONFIG_MODULES >> + struct kernel_trace *iter; >> + struct module *mod = data; >> + >> + if (val != MODULE_STATE_COMING && val != MODULE_STATE_GOING) >> + return 0; >> + mutex_lock(&ktrace_mutex); >> + for (iter = mod->ktrace; iter < mod->ktrace + mod->num_ktrace; iter++) >> + if (val == MODULE_STATE_COMING) >> + add_ktrace(iter); >> + else >> + remove_ktrace(iter, 0); >> + mutex_unlock(&ktrace_mutex); >> +#endif >> + return 0; >> +} >> + >> +static struct notifier_block ktrace_module_nb = { >> + .notifier_call = ktrace_module_notify, >> +}; >> + >> +/* functions for user-space programs to read data from tracing buffer */ >> +static int trace_data_open(struct inode *inode, struct file *filp) >> +{ >> + filp->private_data = inode->i_private; >> + kref_get(&ktrace_kref); >> + return 0; >> +} >> + >> +static void release_trace_buffer(struct kref *kref) >> +{ >> + ring_buffer_free(trace_buffer); >> + trace_buffer = NULL; >> +} >> + >> +static int trace_data_release(struct inode *inode, struct file *filp) >> +{ >> + kref_put(&ktrace_kref, release_trace_buffer); >> + return 0; >> +} >> + >> +static unsigned int trace_data_poll(struct file *filp, poll_table *poll_table) >> +{ >> + struct ring_buffer_per_cpu *cpu_buffer = filp->private_data; >> + if (filp->f_mode & FMODE_READ) { >> + if (!ring_buffer_per_cpu_empty(cpu_buffer)) >> + return POLLIN | POLLRDNORM; >> + poll_wait(filp, &trace_wait, poll_table); >> + if (!ring_buffer_per_cpu_empty(cpu_buffer)) >> + return POLLIN | POLLRDNORM; >> + } >> + return 0; >> +} >> + >> +static int trace_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf) >> +{ >> + struct ring_buffer_per_cpu *cpu_buffer = vma->vm_private_data; >> + pgoff_t pgoff = vmf->pgoff; >> + struct page *page; >> + >> + if (!trace_buffer) >> + return VM_FAULT_OOM; >> + page = ring_buffer_get_page(cpu_buffer, pgoff); >> + if (page == NULL) >> + return VM_FAULT_SIGBUS; >> + get_page(page); >> + vmf->page = page; >> + return 0; >> +} >> + >> +static struct vm_operations_struct trace_data_mmap_ops = { >> + .fault = trace_buf_fault, >> +}; >> + >> +static int trace_data_mmap(struct file *filp, struct vm_area_struct *vma) >> +{ >> + struct ring_buffer_per_cpu *cpu_buffer = filp->private_data; >> + >> + vma->vm_ops = &trace_data_mmap_ops; >> + vma->vm_flags |= VM_DONTEXPAND; >> + vma->vm_private_data = cpu_buffer; >> + return 0; >> +} >> + >> +static int trace_data_ioctl(struct inode *inode, struct file *filp, >> + unsigned int cmd, unsigned long arg) >> +{ >> + u32 __user *argp = (u32 __user *)arg; >> + struct ring_buffer_per_cpu *cpu_buffer = filp->private_data; >> + >> + if (!trace_buffer || !tracedir) >> + return -EINVAL; >> + switch (cmd) { >> + case KTRACE_BUF_GET_SIZE: >> + { >> + unsigned long bufsize; >> + bufsize = ring_buffer_size(trace_buffer); >> + return put_user((u32)bufsize, argp); >> + } >> + case KTRACE_BUF_GET_PRODUCED: >> + return put_user(ring_buffer_get_produced(cpu_buffer), argp); >> + case KTRACE_BUF_GET_CONSUMED: >> + return put_user(ring_buffer_get_consumed(cpu_buffer), argp); >> + case KTRACE_BUF_PUT_CONSUMED: >> + { >> + u32 consumed, consumed_old; >> + int ret; >> + >> + ret = get_user(consumed, argp); >> + if (ret) { >> + printk(KERN_WARNING >> + "error getting consumed value: %d\n", ret); >> + return ret; >> + } >> + consumed_old = ring_buffer_get_consumed(cpu_buffer); >> + if (consumed == consumed_old) >> + return 0; >> + ring_buffer_advance_reader(cpu_buffer, consumed - consumed_old); >> + return 0; >> + } >> + default: >> + return -ENOIOCTLCMD; >> + } >> + return 0; >> +} >> + >> +static const struct file_operations tracedata_file_operations = { >> + .open = trace_data_open, >> + .poll = trace_data_poll, >> + .mmap = trace_data_mmap, >> + .ioctl = trace_data_ioctl, >> + .release = trace_data_release, >> +}; >> + >> +/* function to report the number of lost events due to buffer overflow */ >> +static ssize_t trace_overflow_read(struct file *filp, char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + int ret; >> + char buf[64]; >> + ret = snprintf(buf, 64, "%lu\n", ring_buffer_overruns(trace_buffer)); >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, ret); >> +} >> + >> +static const struct file_operations traceoverflow_file_operations = { >> + .read = trace_overflow_read, >> +}; >> + >> +/* function to re-initialize trace buffer */ >> +static void __trace_buffer_reset(struct file *filp, >> + unsigned long val, size_t *cnt) >> +{ >> + if (val && trace_buffer) >> + ring_buffer_reset(trace_buffer); >> +} >> + >> +static ssize_t trace_buffer_reset(struct file *filp, const char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + return trace_debugfs_write(filp, ubuf, cnt, ppos, >> + __trace_buffer_reset); >> +} >> + >> +static const struct file_operations tracereset_file_operations = { >> + .write = trace_buffer_reset, >> +}; >> + >> +/* >> + * We use debugfs for kernel-user communication. All of the control/info >> + * files are under debugfs/ktrace directory. >> + */ >> +static int create_debugfs(void) >> +{ >> + struct dentry *entry, *bufdir; >> + struct ring_buffer_per_cpu *cpu_buffer; >> + char *tmpname; >> + int cpu; >> + >> + tracedir = debugfs_create_dir("ktrace", NULL); >> + if (!tracedir) { >> + printk(KERN_WARNING "Couldn't create debugfs directory\n"); >> + return -ENOMEM; >> + } >> + >> + /* 'buffers' is the directory that holds trace buffer debugfs files */ >> + bufdir = debugfs_create_dir("buffers", tracedir); >> + if (!bufdir) { >> + printk(KERN_WARNING "Couldn't create 'buffers' directory\n"); >> + return -ENOMEM; >> + } >> + >> + tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL); >> + if (!tmpname) >> + return -ENOMEM; >> + /* create a debugfs file for each cpu buffer */ >> + for_each_possible_cpu(cpu) { >> + snprintf(tmpname, NAME_MAX, "%s%d", "cpu", cpu); >> + cpu_buffer = ring_buffer_cpu(trace_buffer, cpu); >> + entry = debugfs_create_file(tmpname, 0440, bufdir, cpu_buffer, >> + &tracedata_file_operations); >> + if (!entry) { >> + printk(KERN_WARNING >> + "Couldn't create debugfs \'%s\' entry\n", >> + tmpname); >> + return -ENOMEM; >> + } >> + } >> + kfree(tmpname); >> + >> + /* the control file for users to enable/disable global tracing. */ >> + entry = debugfs_create_file("enabled", 0664, tracedir, NULL, >> + &tracecontrol_file_operations); >> + if (!entry) { >> + printk(KERN_WARNING >> + "Couldn't create debugfs 'enabled' entry\n"); >> + return -ENOMEM; >> + } >> + >> + /* >> + * the debugfs file that displays the name, format etc. of every >> + * supported trace event. The file is to be used by the user-space >> + * trace parser to analyze the collected trace data. >> + */ >> + entry = debugfs_create_file("info", 0444, tracedir, NULL, >> + &traceinfo_file_operations); >> + if (!entry) { >> + printk(KERN_WARNING "Couldn't create debugfs 'info' entry\n"); >> + return -ENOMEM; >> + } >> + >> + /* >> + * the debugfs file that reports the number of events >> + * lost due to buffer overflow >> + */ >> + entry = debugfs_create_file("overflow", 0444, tracedir, NULL, >> + &traceoverflow_file_operations); >> + if (!entry) { >> + printk(KERN_WARNING >> + "Couldn't create debugfs 'overflow' entry\n"); >> + return -ENOMEM; >> + } >> + >> + /* the debugfs file that resets trace buffer upon write */ >> + entry = debugfs_create_file("reset", 0220, tracedir, NULL, >> + &tracereset_file_operations); >> + if (!entry) { >> + printk(KERN_WARNING "Couldn't create debugfs 'reset' entry\n"); >> + return -ENOMEM; >> + } >> + >> + /* create the directory that holds the control files for every event */ >> + eventdir = debugfs_create_dir("events", tracedir); >> + if (!eventdir) { >> + printk(KERN_WARNING "Couldn't create 'events' directory\n"); >> + return -ENOMEM; >> + } >> + return 0; >> +} >> + >> +static void remove_debugfs_file(struct dentry *dir, char *name) >> +{ >> + struct dentry *dentry; >> + dentry = lookup_one_len(name, dir, strlen(name)); >> + if (dentry && !IS_ERR(dentry)) { >> + debugfs_remove(dentry); >> + dput(dentry); >> + } >> +} >> + >> +static int remove_debugfs(void) >> +{ >> + struct dentry *bufdir; >> + char *tmpname; >> + int cpu; >> + >> + bufdir = lookup_one_len("buffers", tracedir, strlen("buffers")); >> + if (!bufdir || IS_ERR(bufdir)) >> + return -EIO; >> + tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL); >> + if (!tmpname) >> + return -ENOMEM; >> + for_each_possible_cpu(cpu) { >> + snprintf(tmpname, NAME_MAX, "%s%d", "cpu", cpu); >> + remove_debugfs_file(bufdir, tmpname); >> + } >> + kfree(tmpname); >> + debugfs_remove(bufdir); >> + >> + remove_debugfs_file(tracedir, "enabled"); >> + remove_debugfs_file(tracedir, "info"); >> + debugfs_remove(eventdir); >> + debugfs_remove(tracedir); >> + return 0; >> +} >> + >> +static int __init init_ktrace(void) >> +{ >> + struct kernel_trace *iter; >> + int i, err; >> + >> + ktrace_next_id = 0; >> + kref_set(&ktrace_kref, 1); >> + trace_buffer = ring_buffer_alloc(trace_buf_size, RB_FL_OVERWRITE); >> + if (trace_buffer == NULL) >> + return -ENOMEM; >> + setup_timer(&trace_timer, wakeup_readers, 0); >> + for (i = 0; i < KTRACE_HASH_SIZE; i++) >> + INIT_HLIST_HEAD(&ktrace_table[i]); >> + >> + mutex_lock(&ktrace_mutex); >> + err = create_debugfs(); >> + if (err != 0) >> + goto out; >> + for (iter = __start___ktraces; iter < __stop___ktraces; iter++) >> + add_ktrace(iter); >> + err = register_module_notifier(&ktrace_module_nb); >> +out: >> + mutex_unlock(&ktrace_mutex); >> + return err; >> +} >> +module_init(init_ktrace); >> + >> +static void __exit exit_ktrace(void) >> +{ >> + struct kernel_trace *iter; >> + >> + if (ktrace_enabled) { >> + ktrace_enabled = 0; >> + del_timer_sync(&trace_timer); >> + } >> + mutex_lock(&ktrace_mutex); >> + for (iter = __start___ktraces; iter < __stop___ktraces; iter++) >> + remove_ktrace(iter, 1); >> + unregister_module_notifier(&ktrace_module_nb); >> + remove_debugfs(); >> + mutex_unlock(&ktrace_mutex); >> + >> + kref_put(&ktrace_kref, release_trace_buffer); >> +} > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/