Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757975Ab3CFNvt (ORCPT ); Wed, 6 Mar 2013 08:51:49 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:12285 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755649Ab3CFNvY (ORCPT ); Wed, 6 Mar 2013 08:51:24 -0500 X-Authority-Analysis: v=2.0 cv=H5hZMpki c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=Ciwy3NGCPMMA:10 a=DA3UyxT4lfAA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=PN_71m6708oA:10 a=20KFwNOVAAAA:8 a=3nbZYyFuAAAA:8 a=HsiUkt9cFOICQau9JCQA:9 a=jEp0ucaQiEUA:10 a=EvKJbDF4Ut8A:10 a=jeBq3FmKZ4MA:10 a=D6BXSEMBxAzQ5wFm:21 a=TZ5ixQDsD-zjYP0C:21 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-Id: <20130306135122.335164503@goodmis.org> User-Agent: quilt/0.60-1 Date: Wed, 06 Mar 2013 08:49:17 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Frederic Weisbecker , Hiraku Toyooka Subject: [RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty References: <20130306134916.923746858@goodmis.org> Content-Disposition: inline; filename=0001-tracing-Add-help-of-snapshot-feature-when-snapshot-i.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3669 Lines: 99 From: "Steven Rostedt (Red Hat)" When cat'ing the snapshot file, instead of showing an empty trace header like the trace file does, show how to use the snapshot feature. Also, this is a good place to show if the snapshot has been allocated or not. Users may want to "pre allocate" the snapshot to have a fast "swap" of the current buffer. Otherwise, a swap would be slow and might fail as it would need to allocate the snapshot buffer, and that might fail under tight memory constraints. Here's what it looked like before: # tracer: nop # # entries-in-buffer/entries-written: 0/0 #P:4 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | Here's what it looks like now: # tracer: nop # # # * Snapshot is freed * # # Snapshot commands: # echo 0 > snapshot : Clears and frees snapshot buffer # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated. # Takes a snapshot of the main buffer. # echo 2 > snapshot : Clears snapshot buffer (but does not allocate) # (Doesn't have to be '2' works with any number that # is not a '0' or '1') Cc: Hiraku Toyooka Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index c2e2c23..9e3120b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m) seq_printf(m, "# MAY BE MISSING FUNCTION EVENTS\n"); } +#ifdef CONFIG_TRACER_MAX_TRACE +static void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter) +{ + if (iter->trace->allocated_snapshot) + seq_printf(m, "#\n# * Snapshot is allocated *\n#\n"); + else + seq_printf(m, "#\n# * Snapshot is freed *\n#\n"); + + seq_printf(m, "# Snapshot commands:\n"); + seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n"); + seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n"); + seq_printf(m, "# Takes a snapshot of the main buffer.\n"); + seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)\n"); + seq_printf(m, "# (Doesn't have to be '2' works with any number that\n"); + seq_printf(m, "# is not a '0' or '1')\n"); +} +#else +/* Should never be called */ +static inline void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter) { } +#endif + static int s_show(struct seq_file *m, void *v) { struct trace_iterator *iter = v; @@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v) seq_puts(m, "#\n"); test_ftrace_alive(m); } - if (iter->trace && iter->trace->print_header) + if (iter->snapshot && trace_empty(iter)) + print_snapshot_help(m, iter); + else if (iter->trace && iter->trace->print_header) iter->trace->print_header(m); else trace_default_header(m); -- 1.7.10.4 -- 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/