From: Andrew Morton <akpm@zip.com.au>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: matthew@wil.cx, linux-kernel@vger.kernel.org
Subject: Re: fs/locks.c BKL removal
Date: Fri, 10 May 2002 16:17:29 -0700 [thread overview]
Message-ID: <3CDC5509.DCAF336A@zip.com.au> (raw)
In-Reply-To: <3CDC4037.8040104@us.ibm.com> <3CDC45EF.9000506@us.ibm.com>
Dave Hansen wrote:
>
> As Linus pointed out, a semaphore is probably the wrong way to go.
> The only things that really needs to be protected are the list
> operations themselves.
>
It was I who put the BKL back into locks.c, much to
Matthew's disgust...
The problem was that replacing the BKL with a semaphore
seriously damaged Apache thoughput on 8-way. Apache
was using flock()-based synchronisation and replacing
a spin with a schedule just killed it.
So.. Apache isn't doing that any more, but it is an
instructive case. Replacing the BKL with a semaphore
can sometimes be a very bad thing.
See http://www.uwsg.iu.edu/hypermail/linux/kernel/0010.3/ -
search for "scalability"
-
next prev parent reply other threads:[~2002-05-10 23:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-05-10 21:48 fs/locks.c BKL removal Dave Hansen
2002-05-10 22:13 ` Dave Hansen
2002-05-10 23:17 ` Andrew Morton [this message]
2002-05-11 19:48 ` Matthew Wilcox
2002-05-11 19:45 ` Matthew Wilcox
2002-05-12 1:40 ` Dave Hansen
2002-05-12 2:07 ` Matthew Wilcox
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