From: Ingo Molnar <mingo@kernel.org>
To: Yury Norov <ynorov@caviumnetworks.com>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Akinobu Mita <mita@miraclelinux.com>,
Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH] sched: remove sched_find_first_bit()
Date: Sun, 14 May 2017 20:09:17 +0200 [thread overview]
Message-ID: <20170514180917.bil7xr4bqtfk6fzj@gmail.com> (raw)
In-Reply-To: <20170513010152.13986-1-ynorov@caviumnetworks.com>
* Yury Norov <ynorov@caviumnetworks.com> wrote:
> sched_find_first_bit() is in fact the unrolled version of
> find_first_bit(), which is theoretically faster in some cases.
> But in the kernel it is called only in couple places in
> kernel/sched/rt.c, and both of them are not looking like hot
> paths [...]
They are in terms of scheduling: pick_next_rt_entity() is in the RT scheduling
fastpath.
Which makes me just suspicious of how careful this patch really is:
> that will doubtly achieve measurable benefit from using unrolled version of
> find_first_bit() - there's no hard loops, and the execution path is not really
> short.
... that's really just handwaving. Numbers please.
Thanks,
Ingo
next prev parent reply other threads:[~2017-05-14 18:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-13 1:01 Yury Norov
2017-05-14 18:09 ` Ingo Molnar [this message]
2017-05-15 15:47 ` Yury Norov
2017-05-15 16:06 ` Arnd Bergmann
2017-05-15 16:17 ` Yury Norov
2017-05-15 20:31 ` Arnd Bergmann
2017-05-15 20:58 ` Yury Norov
2017-05-15 21:04 ` Arnd Bergmann
2017-05-16 8:30 ` Ingo Molnar
2017-05-17 12:16 ` Yury Norov
2017-05-18 7:14 ` Ingo Molnar
2017-05-15 14:18 ` Arnd Bergmann
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