Date: Thu, 11 Dec 2008 14:34:24 +0100
From: Jens Axboe <jens.axboe@oracle.com>
To: Vladislav Bolkhovitin <vst@vlnb.net>
Cc: linux-scsi@vger.kernel.org,
       James Bottomley <James.Bottomley@HansenPartnership.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
       Mike Christie <michaelc@cs.wisc.edu>, Jeff Garzik <jeff@garzik.org>,
       Boaz Harrosh <bharrosh@panasas.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org, scst-devel@lists.sourceforge.net,
       Bart Van Assche <bart.vanassche@gmail.com>,
       "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Subject: Re: [PATCH][RFC 13/23]: Export of alloc_io_context() function
Message-ID: <20081211133424.GU23742@kernel.dk>
References: <494009D7.4020602@vlnb.net> <49400F2F.4050603@vlnb.net>
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On Wed, Dec 10 2008, Vladislav Bolkhovitin wrote:
> This patch exports alloc_io_context() function. For performance reasons 
> SCST queues commands using a pool of IO threads. It is considerably 
> better for performance (>30% increase on sequential reads) if threads in 
>   a pool have the same IO context. Since SCST can be built as a module, 
> it needs alloc_io_context() function exported.
> 
> Signed-off-by: Vladislav Bolkhovitin <vst@vlnb.net>
> ---
>   block/blk-ioc.c |    1 +
>   1 file changed, 1 insertion(+)
> 
> diff -upkr linux-2.6.27.2/block/blk-ioc.c linux-2.6.27.2/block/blk-ioc.c
> --- linux-2.6.27.2/block/blk-ioc.c	2008-10-10 02:13:53.000000000 +0400
> +++ linux-2.6.27.2/block/blk-ioc.c	2008-11-25 21:27:01.000000000 +0300
> @@ -105,6 +105,7 @@ struct io_context *alloc_io_context(gfp_
>  
>  	return ret;
>  }
> +EXPORT_SYMBOL(alloc_io_context);

Why is this needed, can't you just use CLONE_IO?

-- 
Jens Axboe

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