From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: riel@redhat.com, linux-kernel@vger.kernel.org
Cc: fweisbec@gmail.com, tglx@linutronix.de, mingo@kernel.org,
luto@amacapital.net, peterz@infradead.org, clark@redhat.com,
eric.dumazet@gmail.com
Subject: Re: [PATCH 0/4 v6] sched,time: reduce nohz_full syscall overhead 40%
Date: Mon, 15 Feb 2016 10:01:29 +0100 [thread overview]
Message-ID: <1455526889.11761.23.camel@gmail.com> (raw)
In-Reply-To: <1455152907-18495-1-git-send-email-riel@redhat.com>
Hi Rik,
On Wed, 2016-02-10 at 20:08 -0500, riel@redhat.com wrote:
> I tested this series with a microbenchmark calling
> an invalid syscall number ten million times in a row,
> on a nohz_full cpu.
>
> Run times for the microbenchmark:
>
> 4.4 3.8 seconds
> 4.5-rc1 3.7 seconds
> 4.5-rc1 + first patch 3.3 seconds
> 4.5-rc1 + first 3 patches 3.1 seconds
> 4.5-rc1 + all patches 2.3 seconds
>
> Same test on a non-NOHZ_FULL, non-housekeeping CPU:
> all kernels 1.86 seconds
I tested 10M stat(".", &buf) calls, and saw a win of ~20% on a
nohz_full cpu. Below are nopreempt vs nohz_full+patches overhead
numbers from my box.
avg
4.4.1-nopreempt 0m1.652s 0m1.633s 0m1.635s 1.640 1.000
nohz_full + patches
nohz_full inactive 0m1.642s 0m1.631s 0m1.629s 1.634 .996
housekeeper CPU 0m2.013s 0m2.012s 0m2.033s 2.019 1.231
nohz_full CPU 0m2.247s 0m2.233s 0m2.239s 2.239 1.365
It still ain't free ;-) but between this set, and all the other work
that has gone in ~recently, it looks one hell of a lot better. That's
not too scary a pricetag.
-Mike
next prev parent reply other threads:[~2016-02-15 9:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-11 1:08 [PATCH 0/4 v6] sched,time: reduce nohz_full syscall overhead 40% riel
2016-02-11 1:08 ` [PATCH 1/4] sched,time: remove non-power-of-two divides from __acct_update_integrals riel
2016-02-29 11:17 ` [tip:sched/core] sched, time: Remove non-power-of-two divides from __acct_update_integrals() tip-bot for Rik van Riel
2016-02-11 1:08 ` [PATCH 2/4] acct,time: change indentation in __acct_update_integrals riel
2016-02-11 1:23 ` Joe Perches
2016-02-29 11:18 ` [tip:sched/core] acct, time: Change indentation in __acct_update_integrals() tip-bot for Rik van Riel
2016-02-11 1:08 ` [PATCH 3/4] time,acct: drop irq save & restore from __acct_update_integrals riel
2016-02-29 11:18 ` [tip:sched/core] time, acct: Drop irq save & restore from __acct_update_integrals() tip-bot for Rik van Riel
2016-02-11 1:08 ` [PATCH 4/4] sched,time: switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity riel
2016-02-29 11:18 ` [tip:sched/core] sched, time: Switch " tip-bot for Rik van Riel
2016-02-29 15:31 ` Frederic Weisbecker
2016-03-01 15:35 ` Frederic Weisbecker
2016-02-15 9:01 ` Mike Galbraith [this message]
2016-02-24 11:16 ` [PATCH 0/4 v6] sched,time: reduce nohz_full syscall overhead 40% Thomas Gleixner
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