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