From: Rik van Riel <riel@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org,
luto@amacapital.net, fweisbec@gmail.com,
Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 2/2] sched,time: call __acct_update_integrals once a jiffy
Date: Fri, 29 Jan 2016 17:43:28 -0500 [thread overview]
Message-ID: <56ABEB10.5060307@redhat.com> (raw)
In-Reply-To: <1454106180-20918-3-git-send-email-riel@redhat.com>
On 01/29/2016 05:23 PM, riel@redhat.com wrote:
> From: Rik van Riel <riel@redhat.com>
> This speeds up
... ok, that changelog got truncated :(
Here is the full version:
Because __acct_update_integrals does nothing unless the time
interval in question exceeds a jiffy, there is no real reason
to call it more than once a jiffy from the syscall, irq, and
guest entry & exit paths.
If tasks get rescheduled frequently, the scheduler will still
update their time statistics normally.
However, longer running tasks with frequent syscall, irq,
or guest entry & exit see a difference with this patch.
A microbenchmark calling an invalid syscall number 10 million
times in a row speeds up an additional 30% over the numbers
with just the previous patch, for a total speedup of about 40%
over 4.4 and 4.5-rc1.
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 + both patches 2.3 seconds
--
All rights reversed
next prev parent reply other threads:[~2016-01-29 22:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 22:22 [PATCH 0/2] sched,time: reduce nohz_full syscall overhead 40% riel
2016-01-29 22:22 ` [PATCH 1/2] sched,time: remove pointless divides from __acct_update_integrals riel
2016-01-29 23:10 ` Peter Zijlstra
2016-01-30 3:36 ` Frederic Weisbecker
2016-01-30 3:47 ` Rik van Riel
2016-01-29 22:23 ` [PATCH 2/2] sched,time: call __acct_update_integrals once a jiffy riel
2016-01-29 22:43 ` Rik van Riel [this message]
2016-01-30 14:20 ` Frederic Weisbecker
2016-01-30 17:53 ` Mike Galbraith
2016-01-30 20:36 ` Frederic Weisbecker
2016-01-31 2:52 ` Mike Galbraith
2016-01-31 5:37 ` Mike Galbraith
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