linux-kernel - Re: [PATCH] fix creating zero sized bio mempools in low memory system

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Message-ID: <20060904124335.GM25434@kernel.dk>
Date:	Mon, 4 Sep 2006 14:43:35 +0200
From:	Jens Axboe <axboe@...nel.dk>
To:	Milan Broz <mbroz@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] fix creating zero sized bio mempools in low memory system

On Mon, Sep 04 2006, Milan Broz wrote:
> In the very low memory systems is in the init_bio call
> scale parameter set to zero and it leads to creating
> zero sized mempool.
> 
> This patch prevents pool_entries parameter become zero,
> so the created pool have at least 1 entry.
> 
> Mempool with 0 entries lead to incorrect behaviour 
> of mempool_free. (Alloc requests are not waken up
> and system stalls in mempool_alloc->ioschedule). 

Good catch, queued. Maybe this is the only such scaling problem,
otherwise it may be a good idea to add a WARN_ON(!min_nr) to the mempool
setup in mm/mempool.c to catch such errors.

-- 
Jens Axboe

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