From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>, riel@redhat.com
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
fweisbec@gmail.com, wanpeng.li@hotmail.com, efault@gmx.de,
tglx@linutronix.de, rkrcmar@redhat.com
Subject: Re: [PATCH 1/5] sched,time: count actually elapsed irq & softirq time
Date: Wed, 22 Jun 2016 12:40:31 +0200 [thread overview]
Message-ID: <2b88a0fd-fdb4-3164-cd0f-9f27afda398c@redhat.com> (raw)
In-Reply-To: <20160621212142.GS30909@twins.programming.kicks-ass.net>
On 21/06/2016 23:21, Peter Zijlstra wrote:
> cputime_to_jiffies is a division, could we not avoid that by doing
> something like:
>
> irq_jiffies = min(irq, jiffies_to_cputime(max_jiffies));
> while (irq_jiffies > cputime_one_jiffy) {
> irq_jiffies -= cputime_one_jiffy;
> cpustat[CPUTIME_IRQ] += cputime_one_jiffy;
> }
>
> assuming that the loop is 'rare' etc.. If not, only do the division on
> that same > cputime_one_jiffy condition.
It's a division by a constant, it ought to become a multiplication. For
64-bit it will, and context tracking is only enabled for 64-bit.
BTW, for 32-bit there's a monster of a macro to turn do_div with
constant divisor into multiplications in include/asm-generic/div64.h.
However, x86-32 doesn't use it.
Paolo
next prev parent reply other threads:[~2016-06-22 10:40 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 16:06 [PATCH 0/5] sched,time: fix irq time accounting with nohz_idle riel
2016-06-16 16:06 ` [PATCH 1/5] sched,time: count actually elapsed irq & softirq time riel
2016-06-16 16:22 ` kbuild test robot
2016-06-21 21:21 ` Peter Zijlstra
2016-06-21 22:20 ` Rik van Riel
2016-06-22 10:40 ` Paolo Bonzini [this message]
2016-06-22 10:52 ` Peter Zijlstra
2016-06-16 16:06 ` [PATCH 2/5] nohz,cputime: remove VTIME_GEN vtime irq time code riel
2016-06-16 16:06 ` [PATCH 3/5] cputime: allow irq time accounting to be selected as an option riel
2016-06-16 16:06 ` [PATCH 4/5] irqtime: add irq type parameter to irqtime_account_irq riel
2016-06-16 16:06 ` [PATCH 5/5] irqtime: drop local_irq_save/restore from irqtime_account_irq riel
2016-06-21 21:49 ` Peter Zijlstra
2016-06-21 22:23 ` Rik van Riel
2016-06-21 22:28 ` Peter Zijlstra
2016-06-21 22:32 ` Rik van Riel
2016-06-22 21:55 ` Rik van Riel
2016-06-23 13:52 ` Paolo Bonzini
2016-06-23 15:24 ` Rik van Riel
-- strict thread matches above, loose matches on Subject: below --
2016-07-13 14:50 [GIT PULL] cputime fixes and cleanups Frederic Weisbecker
2016-07-13 14:50 ` [PATCH 1/5] sched,time: Count actually elapsed irq & softirq time Frederic Weisbecker
2016-08-09 3:59 ` Wanpeng Li
2016-08-09 14:06 ` Rik van Riel
2016-08-09 23:07 ` Wanpeng Li
2016-08-10 7:51 ` Wanpeng Li
2016-08-09 23:25 ` Wanpeng Li
2016-08-09 23:31 ` Wanpeng Li
2016-08-09 23:35 ` Wanpeng Li
2016-08-09 23:39 ` Wanpeng Li
2016-08-10 5:07 ` Rik van Riel
2016-08-10 6:33 ` Wanpeng Li
2016-06-23 2:25 [PATCH v2 0/5] sched,time: fix irq time accounting with nohz_idle riel
2016-06-23 2:25 ` [PATCH 1/5] sched,time: count actually elapsed irq & softirq time riel
2016-06-27 12:25 ` Frederic Weisbecker
2016-06-27 12:50 ` Rik van Riel
2016-06-28 20:56 ` Frederic Weisbecker
2016-06-08 2:29 [PATCH RFC 0/5] sched,time: make irq time accounting work for nohz_idle riel
2016-06-08 2:30 ` [PATCH 1/5] sched,time: count actually elapsed irq & softirq time riel
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=2b88a0fd-fdb4-3164-cd0f-9f27afda398c@redhat.com \
--to=pbonzini@redhat.com \
--cc=efault@gmx.de \
--cc=fweisbec@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=tglx@linutronix.de \
--cc=wanpeng.li@hotmail.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.