From: Alexey Dobriyan <adobriyan@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>,
Denis Vlasenko <vda.linux@googlemail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: + lib-vsprintfc-even-faster-decimal-conversion.patch added to -mm tree
Date: Thu, 19 Mar 2015 15:17:10 +0300 [thread overview]
Message-ID: <CACVxJT9BD=EDuQCzyd9EhLtgg8QAjeYoYAa45E443QBNwhz6NQ@mail.gmail.com> (raw)
In-Reply-To: <20150317150406.f4ec837c6787dc8f3d1661f2@linux-foundation.org>
On Wed, Mar 18, 2015 at 1:04 AM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Mon, 16 Mar 2015 18:19:41 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
>> Rasmus, I redid benchmarks:
>
> tl;dr ;) Is this an ack or a nack?
New code executes slower for some input on one CPU I've benchmarked,
both with -O2 and -Os (Core 2 Duo E6550). The slowdown is in 2-20% range
depending on exact number being converted and is reproducible.
With -O2 "bad" range is roughly 100-70000, with -Os it is 100-1000 and
around 100000.
On another CPU (more modern Core i5-something), new code is uniformly
faster giving advertised 10-20-35-40% speedups (yay!)
The ideal situation is still being
a) one system call to push PIDs into userspace in bulk
(memcpy directly from pid_ns->pidmap[i]),
b) one system call to fetch data in binary to userspace given PID or
set of PIDs,
without all of this string and /proc overhead.
Alexey
next prev parent reply other threads:[~2015-03-19 12:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5500b987.kerYYCYfIffruy3Z%akpm@linux-foundation.org>
2015-03-13 12:49 ` + lib-vsprintfc-even-faster-decimal-conversion.patch added to -mm tree Alexey Dobriyan
2015-03-13 12:56 ` Alexey Dobriyan
2015-03-13 13:00 ` Alexey Dobriyan
2015-03-13 23:53 ` Rasmus Villemoes
2015-03-14 9:21 ` Alexey Dobriyan
2015-03-16 15:19 ` Alexey Dobriyan
2015-03-17 22:04 ` Andrew Morton
2015-03-19 12:17 ` Alexey Dobriyan [this message]
2015-03-19 22:15 ` Rasmus Villemoes
2015-03-22 17:29 ` Denys Vlasenko
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