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Date: Thu, 25 Oct 2001 19:33:43 +0200
From: Jens Axboe <axboe@suse.de>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Zlatko Calusic <zlatko.calusic@iskon.hr>,
        Marcelo Tosatti <marcelo@conectiva.com.br>, linux-mm@kvack.org,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: xmm2 - monitor Linux MM active/inactive lists graphically
Message-ID: <20011025193343.K4795@suse.de>
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On Thu, Oct 25 2001, Linus Torvalds wrote:
> 
> On 25 Oct 2001, Zlatko Calusic wrote:
> >
> > Yes, I definitely have DMA turned ON. All parameters are OK. :)
> 
> I suspect it may just be that "queue_nr_requests"/"batch_count" is
> different in -ac: what happens if you tweak them to the same values?
> 
> (See drivers/block/ll_rw_block.c)
> 
> I think -ac made the queues a bit deeper the regular kernel does 128
> requests and a batch-count of 16, I _think_ -ac does something like "2
> requests per megabyte" and batch_count=32, so if you have 512MB you should
> try with
> 
> 	queue_nr_requests = 1024
> 	batch_count = 32

Right, -ac keeps the elevator flow control and proper queue sizes.

-- 
Jens Axboe

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