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Re: Odd pagebuf message

To: Steve Lord <lord@xxxxxxx>
Subject: Re: Odd pagebuf message
From: Jens Axboe <axboe@xxxxxxx>
Date: Mon, 17 Dec 2001 16:20:14 +0100
Cc: Eric Sandeen <sandeen@xxxxxxx>, David Chambers <davidc@xxxxxxxxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <1008601736.24141.0.camel@jen.americas.sgi.com>
References: <200112161757.fBGHvPW21023@pinga.salk.edu> <Pine.LNX.4.33.0112161927200.12284-100000@chuckle.americas.sgi.com> <20011217110745.GH4587@suse.de> <1008601736.24141.0.camel@jen.americas.sgi.com>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Mon, Dec 17 2001, Steve Lord wrote:
> On Mon, 2001-12-17 at 05:07, Jens Axboe wrote:
> > On Sun, Dec 16 2001, Eric Sandeen wrote:
> > > Congratulations, you appear to be the world's first user of the
> > > pre-allocated buffer head pool in pagebuf!  :)
> > > 
> > > when pagebuf initializes, it sets aside a handful of buffer heads to use
> > > in "emergency" situations, i.e. if it tries to allocate a buffer head and
> > > fails.  If this happens, it takes one from this pre-allocated pool
> > > instead.  If normal allocation fails, _and_ the pre-allocated pool is
> > > empty, that thread will sleep until buffer heads get replaced in the
> > > pre-allocated pool - this is what happened to you.  The thread gets woken
> > > up and picks up where it left off as soon as it is able to get a
> > > buffer head allocated from the pool.
> > 
> > BTW, in your 2.5 tree please drop such private pre-allocations and use
> > the mempool_* interface. bio/bio_vec allocations and highmem are already
> > using them :-)
> 
> It's already gone Jens.

Very cool Steve, good job :-)

-- 
Jens Axboe


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