Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753595Ab2KSPyn (ORCPT ); Mon, 19 Nov 2012 10:54:43 -0500 Received: from relay2.sgi.com ([192.48.179.30]:35627 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753492Ab2KSPym (ORCPT ); Mon, 19 Nov 2012 10:54:42 -0500 From: Nathan Zimmer Cc: davej@redhat.com, Nathan Zimmer , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] procfs: /proc/schedstat fails on very very large machines. Date: Mon, 19 Nov 2012 09:54:39 -0600 Message-Id: <1353340480-31962-2-git-send-email-nzimmer@sgi.com> X-Mailer: git-send-email 1.6.0.2 In-Reply-To: <1353340480-31962-1-git-send-email-nzimmer@sgi.com> References: <1353340480-31962-1-git-send-email-nzimmer@sgi.com> To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3488 Lines: 132 On systems with 4096 cores doing a cat /proc/schedstat fails. We are trying to push all the data into a single kmalloc buffer. The issue is on these very large machines all the data will not fit in 4mb. The failure can occur on smaller systems when memory fragmentation is high. A better solution is to not us the single_open mechanism but to provide our own seq_operations. The output should be identical to previous version and thus not need the version number. Signed-off-by: Nathan Zimmer CC: Ingo Molnar CC: Peter Zijlstra CC: linux-kernel@vger.kernel.org Reported-by: Dave Jones --- kernel/sched/stats.c | 73 ++++++++++++++++++++++++++++++++++++------------- 1 files changed, 53 insertions(+), 20 deletions(-) diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c index 903ffa9..33a85c9 100644 --- a/kernel/sched/stats.c +++ b/kernel/sched/stats.c @@ -21,9 +21,13 @@ static int show_schedstat(struct seq_file *seq, void *v) if (mask_str == NULL) return -ENOMEM; - seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION); - seq_printf(seq, "timestamp %lu\n", jiffies); - for_each_online_cpu(cpu) { + if (v == (void *)1) { + seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION); + seq_printf(seq, "timestamp %lu\n", jiffies); + } else { + + cpu = (unsigned long)(v - 2); + struct rq *rq = cpu_rq(cpu); #ifdef CONFIG_SMP struct sched_domain *sd; @@ -72,35 +76,64 @@ static int show_schedstat(struct seq_file *seq, void *v) } rcu_read_unlock(); #endif + kfree(mask_str); } - kfree(mask_str); return 0; } -static int schedstat_open(struct inode *inode, struct file *file) +static void *schedstat_start(struct seq_file *file, loff_t *offset) { - unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32); - char *buf = kmalloc(size, GFP_KERNEL); - struct seq_file *m; - int res; + unsigned long n = *offset; - if (!buf) - return -ENOMEM; - res = single_open(file, show_schedstat, NULL); - if (!res) { - m = file->private_data; - m->buf = buf; - m->size = size; - } else - kfree(buf); - return res; + if (n == 0) + return (void *) 1; + + n--; + + if (n > 0) + n = cpumask_next(n - 1, cpu_online_mask); + else + n = cpumask_first(cpu_online_mask); + + *offset = n + 1; + + if (n < nr_cpu_ids) + return (void *)(unsigned long)(n + 2); + return NULL; +} + +static void *schedstat_next(struct seq_file *file, void *data, loff_t *offset) +{ + (*offset)++; + return schedstat_start(file, offset); +} + +static void schedstat_stop(struct seq_file *file, void *data) +{ +} + +static const struct seq_operations schedstat_sops = { + .start = schedstat_start, + .next = schedstat_next, + .stop = schedstat_stop, + .show = show_schedstat, +}; + +static int schedstat_open(struct inode *inode, struct file *file) +{ + return seq_open(file, &schedstat_sops); } +static int schedstat_release(struct inode *inode, struct file *file) +{ + return 0; +}; + static const struct file_operations proc_schedstat_operations = { .open = schedstat_open, .read = seq_read, .llseek = seq_lseek, - .release = single_release, + .release = schedstat_release, }; static int __init proc_schedstat_init(void) -- 1.6.0.2 -- 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/