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![Tejun Heo](/assets/img/avatar_default.png)
percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
297 lines
7.7 KiB
C
297 lines
7.7 KiB
C
/*
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* latencytop.c: Latency display infrastructure
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*
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* (C) Copyright 2008 Intel Corporation
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* Author: Arjan van de Ven <arjan@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*/
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/*
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* CONFIG_LATENCYTOP enables a kernel latency tracking infrastructure that is
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* used by the "latencytop" userspace tool. The latency that is tracked is not
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* the 'traditional' interrupt latency (which is primarily caused by something
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* else consuming CPU), but instead, it is the latency an application encounters
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* because the kernel sleeps on its behalf for various reasons.
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*
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* This code tracks 2 levels of statistics:
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* 1) System level latency
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* 2) Per process latency
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*
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* The latency is stored in fixed sized data structures in an accumulated form;
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* if the "same" latency cause is hit twice, this will be tracked as one entry
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* in the data structure. Both the count, total accumulated latency and maximum
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* latency are tracked in this data structure. When the fixed size structure is
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* full, no new causes are tracked until the buffer is flushed by writing to
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* the /proc file; the userspace tool does this on a regular basis.
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*
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* A latency cause is identified by a stringified backtrace at the point that
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* the scheduler gets invoked. The userland tool will use this string to
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* identify the cause of the latency in human readable form.
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*
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* The information is exported via /proc/latency_stats and /proc/<pid>/latency.
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* These files look like this:
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*
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* Latency Top version : v0.1
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* 70 59433 4897 i915_irq_wait drm_ioctl vfs_ioctl do_vfs_ioctl sys_ioctl
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* | | | |
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* | | | +----> the stringified backtrace
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* | | +---------> The maximum latency for this entry in microseconds
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* | +--------------> The accumulated latency for this entry (microseconds)
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* +-------------------> The number of times this entry is hit
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*
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* (note: the average latency is the accumulated latency divided by the number
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* of times)
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*/
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#include <linux/latencytop.h>
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#include <linux/kallsyms.h>
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#include <linux/seq_file.h>
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#include <linux/notifier.h>
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#include <linux/spinlock.h>
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#include <linux/proc_fs.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/list.h>
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#include <linux/stacktrace.h>
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static DEFINE_SPINLOCK(latency_lock);
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#define MAXLR 128
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static struct latency_record latency_record[MAXLR];
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int latencytop_enabled;
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void clear_all_latency_tracing(struct task_struct *p)
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{
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unsigned long flags;
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if (!latencytop_enabled)
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return;
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spin_lock_irqsave(&latency_lock, flags);
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memset(&p->latency_record, 0, sizeof(p->latency_record));
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p->latency_record_count = 0;
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spin_unlock_irqrestore(&latency_lock, flags);
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}
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static void clear_global_latency_tracing(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&latency_lock, flags);
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memset(&latency_record, 0, sizeof(latency_record));
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spin_unlock_irqrestore(&latency_lock, flags);
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}
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static void __sched
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account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat)
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{
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int firstnonnull = MAXLR + 1;
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int i;
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if (!latencytop_enabled)
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return;
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/* skip kernel threads for now */
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if (!tsk->mm)
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return;
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for (i = 0; i < MAXLR; i++) {
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int q, same = 1;
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/* Nothing stored: */
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if (!latency_record[i].backtrace[0]) {
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if (firstnonnull > i)
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firstnonnull = i;
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continue;
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}
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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unsigned long record = lat->backtrace[q];
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if (latency_record[i].backtrace[q] != record) {
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same = 0;
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break;
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}
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/* 0 and ULONG_MAX entries mean end of backtrace: */
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if (record == 0 || record == ULONG_MAX)
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break;
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}
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if (same) {
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latency_record[i].count++;
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latency_record[i].time += lat->time;
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if (lat->time > latency_record[i].max)
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latency_record[i].max = lat->time;
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return;
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}
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}
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i = firstnonnull;
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if (i >= MAXLR - 1)
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return;
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/* Allocted a new one: */
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memcpy(&latency_record[i], lat, sizeof(struct latency_record));
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}
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/*
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* Iterator to store a backtrace into a latency record entry
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*/
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static inline void store_stacktrace(struct task_struct *tsk,
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struct latency_record *lat)
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{
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struct stack_trace trace;
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memset(&trace, 0, sizeof(trace));
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trace.max_entries = LT_BACKTRACEDEPTH;
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trace.entries = &lat->backtrace[0];
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save_stack_trace_tsk(tsk, &trace);
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}
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/**
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* __account_scheduler_latency - record an occured latency
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* @tsk - the task struct of the task hitting the latency
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* @usecs - the duration of the latency in microseconds
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* @inter - 1 if the sleep was interruptible, 0 if uninterruptible
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*
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* This function is the main entry point for recording latency entries
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* as called by the scheduler.
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*
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* This function has a few special cases to deal with normal 'non-latency'
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* sleeps: specifically, interruptible sleep longer than 5 msec is skipped
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* since this usually is caused by waiting for events via select() and co.
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*
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* Negative latencies (caused by time going backwards) are also explicitly
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* skipped.
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*/
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void __sched
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__account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
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{
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unsigned long flags;
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int i, q;
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struct latency_record lat;
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/* Long interruptible waits are generally user requested... */
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if (inter && usecs > 5000)
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return;
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/* Negative sleeps are time going backwards */
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/* Zero-time sleeps are non-interesting */
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if (usecs <= 0)
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return;
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memset(&lat, 0, sizeof(lat));
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lat.count = 1;
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lat.time = usecs;
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lat.max = usecs;
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store_stacktrace(tsk, &lat);
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spin_lock_irqsave(&latency_lock, flags);
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account_global_scheduler_latency(tsk, &lat);
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/*
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* short term hack; if we're > 32 we stop; future we recycle:
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*/
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tsk->latency_record_count++;
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if (tsk->latency_record_count >= LT_SAVECOUNT)
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goto out_unlock;
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for (i = 0; i < LT_SAVECOUNT; i++) {
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struct latency_record *mylat;
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int same = 1;
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mylat = &tsk->latency_record[i];
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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unsigned long record = lat.backtrace[q];
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if (mylat->backtrace[q] != record) {
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same = 0;
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break;
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}
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/* 0 and ULONG_MAX entries mean end of backtrace: */
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if (record == 0 || record == ULONG_MAX)
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break;
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}
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if (same) {
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mylat->count++;
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mylat->time += lat.time;
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if (lat.time > mylat->max)
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mylat->max = lat.time;
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goto out_unlock;
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}
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}
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/* Allocated a new one: */
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i = tsk->latency_record_count;
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memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
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out_unlock:
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spin_unlock_irqrestore(&latency_lock, flags);
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}
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static int lstats_show(struct seq_file *m, void *v)
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{
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int i;
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seq_puts(m, "Latency Top version : v0.1\n");
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for (i = 0; i < MAXLR; i++) {
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if (latency_record[i].backtrace[0]) {
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int q;
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seq_printf(m, "%i %lu %lu ",
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latency_record[i].count,
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latency_record[i].time,
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latency_record[i].max);
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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char sym[KSYM_SYMBOL_LEN];
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char *c;
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if (!latency_record[i].backtrace[q])
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break;
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if (latency_record[i].backtrace[q] == ULONG_MAX)
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break;
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sprint_symbol(sym, latency_record[i].backtrace[q]);
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c = strchr(sym, '+');
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if (c)
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*c = 0;
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seq_printf(m, "%s ", sym);
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}
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seq_printf(m, "\n");
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}
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}
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return 0;
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}
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static ssize_t
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lstats_write(struct file *file, const char __user *buf, size_t count,
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loff_t *offs)
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{
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clear_global_latency_tracing();
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return count;
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}
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static int lstats_open(struct inode *inode, struct file *filp)
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{
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return single_open(filp, lstats_show, NULL);
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}
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static const struct file_operations lstats_fops = {
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.open = lstats_open,
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.read = seq_read,
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.write = lstats_write,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int __init init_lstats_procfs(void)
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{
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proc_create("latency_stats", 0644, NULL, &lstats_fops);
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return 0;
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}
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device_initcall(init_lstats_procfs);
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