From: Thomas Gleixner <tglx@linutronix.de>
To: riel@redhat.com
Cc: linux-kernel@vger.kernel.org, fweisbec@gmail.com,
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: Wed, 24 Feb 2016 12:16:19 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1602241215590.3670@nanos> (raw)
In-Reply-To: <1455152907-18495-1-git-send-email-riel@redhat.com>
On Wed, 10 Feb 2016, riel@redhat.com wrote:
> (v6: make VIRT_CPU_ACCOUNTING_GEN jiffy granularity)
>
> Running with nohz_full introduces a fair amount of overhead.
> Specifically, various things that are usually done from the
> timer interrupt are now done at syscall, irq, and guest
> entry and exit times.
>
> However, some of the code that is called every single time
> has only ever worked at jiffy resolution. The code in
> __acct_update_integrals was also doing some unnecessary
> calculations.
>
> Getting rid of the unnecessary calculations, without
> changing any of the functionality in __acct_update_integrals
> gets us about an 11% win.
>
> Not calling the time statistics updating code more than
> once per jiffy, like is done on housekeeping CPUs and on
> all the CPUs of a non-nohz_full system, shaves off a
> further 30%.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
prev parent reply other threads:[~2016-02-24 11:17 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 ` [PATCH 0/4 v6] sched,time: reduce nohz_full syscall overhead 40% Mike Galbraith
2016-02-24 11:16 ` Thomas Gleixner [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.11.1602241215590.3670@nanos \
--to=tglx@linutronix.de \
--cc=clark@redhat.com \
--cc=eric.dumazet@gmail.com \
--cc=fweisbec@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).