From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: KOSAKI Motohiro
<kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
Cc: Bryan Donlan <bdonlan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Ulrich Drepper <drepper-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Timo Sirainen <tss-X3B1VOXEql0@public.gmane.org>
Subject: Re: [resend][PATCH] Added PR_SET_PROCTITLE_AREA option for prctl()
Date: Mon, 12 Oct 2009 12:22:46 -0700 [thread overview]
Message-ID: <20091012122246.a941013b.akpm@linux-foundation.org> (raw)
In-Reply-To: <20091013022335.C741.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
On Tue, 13 Oct 2009 04:03:45 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org> wrote:
> > Start simple. What's wrong with mutex_lock() on the reader and writer
> > sides? rwsems might be OK too.
> >
> > In both cases we should think about whether persistent readers can
> > block the writer excessively though.
>
> I thought your mention seems reasonable. then I mesured various locking
> performance.
>
> no-contention read-read contetion read-write contention
> w/o patch 4627 ms 7575 ms N/A
> mutex 5717 ms 33872 ms (!) 14793 ms
> rw-semaphoe 6846 ms 10734 ms 36156 ms (!)
> seqlock 4754 ms 7558 ms 9373 ms
>
> Umm, seqlock is significantly better than other.
Sure, but even the worst case there is 1,000,000 operations in 34
seconds (yes?). 33 microseconds for a /proc read while under a specific
local DoS attack is OK!
If so then all implementations are acceptable and we should choose the
simplest, most-obviously-correct one.
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Bryan Donlan <bdonlan@gmail.com>,
linux-kernel@vger.kernel.org, Ulrich Drepper <drepper@redhat.com>,
linux-api@vger.kernel.org, Timo Sirainen <tss@iki.fi>
Subject: Re: [resend][PATCH] Added PR_SET_PROCTITLE_AREA option for prctl()
Date: Mon, 12 Oct 2009 12:22:46 -0700 [thread overview]
Message-ID: <20091012122246.a941013b.akpm@linux-foundation.org> (raw)
In-Reply-To: <20091013022335.C741.A69D9226@jp.fujitsu.com>
On Tue, 13 Oct 2009 04:03:45 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> > Start simple. What's wrong with mutex_lock() on the reader and writer
> > sides? rwsems might be OK too.
> >
> > In both cases we should think about whether persistent readers can
> > block the writer excessively though.
>
> I thought your mention seems reasonable. then I mesured various locking
> performance.
>
> no-contention read-read contetion read-write contention
> w/o patch 4627 ms 7575 ms N/A
> mutex 5717 ms 33872 ms (!) 14793 ms
> rw-semaphoe 6846 ms 10734 ms 36156 ms (!)
> seqlock 4754 ms 7558 ms 9373 ms
>
> Umm, seqlock is significantly better than other.
Sure, but even the worst case there is 1,000,000 operations in 34
seconds (yes?). 33 microseconds for a /proc read while under a specific
local DoS attack is OK!
If so then all implementations are acceptable and we should choose the
simplest, most-obviously-correct one.
next prev parent reply other threads:[~2009-10-12 19:22 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-09 4:50 [resend][PATCH] Added PR_SET_PROCTITLE_AREA option for prctl() KOSAKI Motohiro
2009-10-09 4:50 ` KOSAKI Motohiro
2009-10-10 0:13 ` Andrew Morton
2009-10-10 2:22 ` Bryan Donlan
[not found] ` <3e8340490910091922g7891b31al649e91f15ffae687-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2009-10-10 2:42 ` Andrew Morton
2009-10-10 2:42 ` Andrew Morton
[not found] ` <20091009194250.eb76e338.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2009-10-10 2:57 ` Bryan Donlan
2009-10-10 2:57 ` Bryan Donlan
2009-10-10 6:32 ` KOSAKI Motohiro
[not found] ` <2f11576a0910092332s6e0e3dcs35864e3a2164be0-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2009-10-10 6:39 ` Andrew Morton
2009-10-10 6:39 ` Andrew Morton
2009-10-12 19:03 ` KOSAKI Motohiro
[not found] ` <20091013022335.C741.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2009-10-12 19:22 ` Andrew Morton [this message]
2009-10-12 19:22 ` Andrew Morton
[not found] ` <20091012122246.a941013b.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2009-10-13 0:03 ` KOSAKI Motohiro
2009-10-13 0:03 ` KOSAKI Motohiro
2009-10-10 7:11 ` Bryan Donlan
[not found] ` <3e8340490910100011u17497293o613334c64f1543c8-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2009-10-12 19:03 ` KOSAKI Motohiro
2009-10-12 19:03 ` KOSAKI Motohiro
[not found] ` <20091013031853.C744.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2009-10-12 19:33 ` Bryan Donlan
2009-10-12 19:33 ` Bryan Donlan
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