From: Anton Blanchard <anton@samba.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com,
mikey@neuling.org, cyrilbur@gmail.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/64: Use tick accounting by default
Date: Mon, 22 May 2017 15:13:13 +1000 [thread overview]
Message-ID: <20170522151313.3f60aca2@kryten> (raw)
In-Reply-To: <87shjxsf0i.fsf@concordia.ellerman.id.au>
Hi Michael,
> > ppc64 is the only architecture that turns on
> > VIRT_CPU_ACCOUNTING_NATIVE by default. The overhead of this option
> > is extremely high - a context switch microbenchmark using
> > sched_yield() is almost 20% slower.
>
> Running on what? It should all be nop'ed out unless you're on a
> platform that needs it (SPLPAR).
POWERNV native. We don't nop out all the vtime_account_* gunk do we? It
is all those functions that are a large part of the problem.
> > To get finer grained user/hardirq/softirq statitics, the
> > IRQ_TIME_ACCOUNTING option can be used instead, which has much lower
> > overhead.
>
> Can it? We don't select HAVE_IRQ_TIME_ACCOUNTING, so AFAICS it can't
> be enabled.
I have a separate patch to enable it.
> Doesn't dropping this mean we never count stolen time?
Perhaps. Do we have any applications left that care?
Anton
next prev parent reply other threads:[~2017-05-22 5:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-19 14:41 [PATCH] powerpc/64: Use tick accounting by default Anton Blanchard
2017-05-22 4:15 ` Michael Ellerman
2017-05-22 4:46 ` Nicholas Piggin
2017-05-22 5:13 ` Anton Blanchard [this message]
2022-05-25 8:36 ` Christophe Leroy
2017-05-22 7:26 ` Christophe LEROY
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