From: Andrea Arcangeli <aarcange@redhat.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
Tim LaBerge <tim.laberge@quantum.com>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Subject: Re: Corruption with O_DIRECT and unaligned user buffers
Date: Sat, 20 Dec 2008 16:55:36 +0100 [thread overview]
Message-ID: <20081220155536.GD6383@random.random> (raw)
In-Reply-To: <20081219161911.dcf15331.kamezawa.hiroyu@jp.fujitsu.com>
On Fri, Dec 19, 2008 at 04:19:11PM +0900, KAMEZAWA Hiroyuki wrote:
> Result of cost-of-fork() on ia64.
> ==
> size of memory before after
> Anon=1M , 0.07ms, 0.08ms
> Anon=10M , 0.17ms, 0.22ms
> Anon=100M , 1.15ms, 1.64ms
> Anon=1000M , 11.5ms, 15.821ms
> ==
>
> fork() cost is 135% when the process has 1G of Anon.
Not sure where the 135% number comes from. The above number shows a
performance decrease of 27% or a time increase of 37% which I hope is
inline with the overhead introduced by the TestSetPageLocked in the
fast path (which I didn't expect to be so bad), but that it's almost
trivial to eliminate with a smb_wmb in add_to_swap_cache and a smb_rmb
in fork. So we'll need to repeat this measurement after replacing the
TestSetPageLocked with smb_rmb.
next prev parent reply other threads:[~2008-12-20 15:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-14 17:04 Corruption with O_DIRECT and unaligned user buffers Tim LaBerge
2008-11-19 4:25 ` Nick Piggin
2008-11-19 6:52 ` Nick Piggin
2008-11-19 16:58 ` Andrea Arcangeli
2008-12-18 15:29 ` Andrea Arcangeli
2008-12-19 2:21 ` KAMEZAWA Hiroyuki
2008-12-19 5:06 ` KAMEZAWA Hiroyuki
2008-12-19 6:34 ` KOSAKI Motohiro
2008-12-20 16:02 ` Andrea Arcangeli
2008-12-19 7:19 ` KAMEZAWA Hiroyuki
2008-12-19 7:44 ` Li Zefan
2008-12-19 8:45 ` Li Zefan
2008-12-19 20:27 ` Andrea Arcangeli
2008-12-20 15:55 ` Andrea Arcangeli [this message]
2008-12-19 11:51 ` Li Zefan
2008-12-19 12:14 ` KOSAKI Motohiro
2008-12-19 12:58 ` Hugh Dickins
2008-12-19 20:34 ` Andrea Arcangeli
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