linux/kernel/tsacct.c
Rik van Riel 9344c92c2e time, acct: Drop irq save & restore from __acct_update_integrals()
It looks like all the call paths that lead to __acct_update_integrals()
already have irqs disabled, and __acct_update_integrals() does not need
to disable irqs itself.

This is very convenient since about half the CPU time left in this
function was spent in local_irq_save alone.

Performance of a microbenchmark that calls an invalid syscall
ten million times in a row on a nohz_full CPU improves 21% vs.
4.5-rc1 with both the removal of divisions from __acct_update_integrals()
and this patch, with runtime dropping from 3.7 to 2.9 seconds.

With these patches applied, the highest remaining cpu user in
the trace is native_sched_clock, which is addressed in the next
patch.

For testing purposes I stuck a WARN_ON(!irqs_disabled()) test
in __acct_update_integrals(). It did not trigger.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: clark@redhat.com
Cc: eric.dumazet@gmail.com
Cc: fweisbec@gmail.com
Cc: luto@amacapital.net
Link: http://lkml.kernel.org/r/1455152907-18495-4-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-29 09:53:09 +01:00

187 lines
5.1 KiB
C

/*
* tsacct.c - System accounting over taskstats interface
*
* Copyright (C) Jay Lan, <jlan@sgi.com>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/tsacct_kern.h>
#include <linux/acct.h>
#include <linux/jiffies.h>
#include <linux/mm.h>
/*
* fill in basic accounting fields
*/
void bacct_add_tsk(struct user_namespace *user_ns,
struct pid_namespace *pid_ns,
struct taskstats *stats, struct task_struct *tsk)
{
const struct cred *tcred;
cputime_t utime, stime, utimescaled, stimescaled;
u64 delta;
BUILD_BUG_ON(TS_COMM_LEN < TASK_COMM_LEN);
/* calculate task elapsed time in nsec */
delta = ktime_get_ns() - tsk->start_time;
/* Convert to micro seconds */
do_div(delta, NSEC_PER_USEC);
stats->ac_etime = delta;
/* Convert to seconds for btime */
do_div(delta, USEC_PER_SEC);
stats->ac_btime = get_seconds() - delta;
if (thread_group_leader(tsk)) {
stats->ac_exitcode = tsk->exit_code;
if (tsk->flags & PF_FORKNOEXEC)
stats->ac_flag |= AFORK;
}
if (tsk->flags & PF_SUPERPRIV)
stats->ac_flag |= ASU;
if (tsk->flags & PF_DUMPCORE)
stats->ac_flag |= ACORE;
if (tsk->flags & PF_SIGNALED)
stats->ac_flag |= AXSIG;
stats->ac_nice = task_nice(tsk);
stats->ac_sched = tsk->policy;
stats->ac_pid = task_pid_nr_ns(tsk, pid_ns);
rcu_read_lock();
tcred = __task_cred(tsk);
stats->ac_uid = from_kuid_munged(user_ns, tcred->uid);
stats->ac_gid = from_kgid_munged(user_ns, tcred->gid);
stats->ac_ppid = pid_alive(tsk) ?
task_tgid_nr_ns(rcu_dereference(tsk->real_parent), pid_ns) : 0;
rcu_read_unlock();
task_cputime(tsk, &utime, &stime);
stats->ac_utime = cputime_to_usecs(utime);
stats->ac_stime = cputime_to_usecs(stime);
task_cputime_scaled(tsk, &utimescaled, &stimescaled);
stats->ac_utimescaled = cputime_to_usecs(utimescaled);
stats->ac_stimescaled = cputime_to_usecs(stimescaled);
stats->ac_minflt = tsk->min_flt;
stats->ac_majflt = tsk->maj_flt;
strncpy(stats->ac_comm, tsk->comm, sizeof(stats->ac_comm));
}
#ifdef CONFIG_TASK_XACCT
#define KB 1024
#define MB (1024*KB)
#define KB_MASK (~(KB-1))
/*
* fill in extended accounting fields
*/
void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
{
struct mm_struct *mm;
/* convert pages-nsec/1024 to Mbyte-usec, see __acct_update_integrals */
stats->coremem = p->acct_rss_mem1 * PAGE_SIZE;
do_div(stats->coremem, 1000 * KB);
stats->virtmem = p->acct_vm_mem1 * PAGE_SIZE;
do_div(stats->virtmem, 1000 * KB);
mm = get_task_mm(p);
if (mm) {
/* adjust to KB unit */
stats->hiwater_rss = get_mm_hiwater_rss(mm) * PAGE_SIZE / KB;
stats->hiwater_vm = get_mm_hiwater_vm(mm) * PAGE_SIZE / KB;
mmput(mm);
}
stats->read_char = p->ioac.rchar & KB_MASK;
stats->write_char = p->ioac.wchar & KB_MASK;
stats->read_syscalls = p->ioac.syscr & KB_MASK;
stats->write_syscalls = p->ioac.syscw & KB_MASK;
#ifdef CONFIG_TASK_IO_ACCOUNTING
stats->read_bytes = p->ioac.read_bytes & KB_MASK;
stats->write_bytes = p->ioac.write_bytes & KB_MASK;
stats->cancelled_write_bytes = p->ioac.cancelled_write_bytes & KB_MASK;
#else
stats->read_bytes = 0;
stats->write_bytes = 0;
stats->cancelled_write_bytes = 0;
#endif
}
#undef KB
#undef MB
static void __acct_update_integrals(struct task_struct *tsk,
cputime_t utime, cputime_t stime)
{
cputime_t time, dtime;
u64 delta;
if (!likely(tsk->mm))
return;
time = stime + utime;
dtime = time - tsk->acct_timexpd;
/* Avoid division: cputime_t is often in nanoseconds already. */
delta = cputime_to_nsecs(dtime);
if (delta < TICK_NSEC)
return;
tsk->acct_timexpd = time;
/*
* Divide by 1024 to avoid overflow, and to avoid division.
* The final unit reported to userspace is Mbyte-usecs,
* the rest of the math is done in xacct_add_tsk.
*/
tsk->acct_rss_mem1 += delta * get_mm_rss(tsk->mm) >> 10;
tsk->acct_vm_mem1 += delta * tsk->mm->total_vm >> 10;
}
/**
* acct_update_integrals - update mm integral fields in task_struct
* @tsk: task_struct for accounting
*/
void acct_update_integrals(struct task_struct *tsk)
{
cputime_t utime, stime;
unsigned long flags;
local_irq_save(flags);
task_cputime(tsk, &utime, &stime);
__acct_update_integrals(tsk, utime, stime);
local_irq_restore(flags);
}
/**
* acct_account_cputime - update mm integral after cputime update
* @tsk: task_struct for accounting
*/
void acct_account_cputime(struct task_struct *tsk)
{
__acct_update_integrals(tsk, tsk->utime, tsk->stime);
}
/**
* acct_clear_integrals - clear the mm integral fields in task_struct
* @tsk: task_struct whose accounting fields are cleared
*/
void acct_clear_integrals(struct task_struct *tsk)
{
tsk->acct_timexpd = 0;
tsk->acct_rss_mem1 = 0;
tsk->acct_vm_mem1 = 0;
}
#endif