linux-kernel - Re: [00/41] Large Blocksize Support V7 (adds memmap support)

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Message-ID: <20070916224022.GA3573@lazybastard.org>
Date:	Mon, 17 Sep 2007 00:40:22 +0200
From:	Jörn Engel <joern@...fs.org>
To:	Goswin von Brederlow <brederlo@...ormatik.uni-tuebingen.de>
Cc:	Joern Engel <joern@...fs.org>, Andrea Arcangeli <andrea@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Christoph Lameter <clameter@....com>,
	torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
	Mel Gorman <mel@...net.ie>,
	William Lee Irwin III <wli@...omorphy.com>,
	David Chinner <dgc@....com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Badari Pulavarty <pbadari@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Fengguang Wu <fengguang.wu@...il.com>,
	swin wang <wangswin@...il.com>, totty.lu@...il.com,
	hugh@...itas.com
Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support)

On Mon, 17 September 2007 00:06:24 +0200, Goswin von Brederlow wrote:
> 
> How probable is it that the dentry is needed again? If you copy it and
> it is not needed then you wasted time. If you throw it out and it is
> needed then you wasted time too. Depending on the probability one of
> the two is cheaper overall. Idealy I would throw away dentries that
> haven't been accessed recently and copy recently used ones.
> 
> How much of a systems ram is spend on dentires? How much on task
> structures? Does anyone have some stats on that? If it is <10% of the
> total ram combined then I don't see much point in moving them. Just
> keep them out of the way of users memory so the buddy system can work
> effectively.

As usual, the answer is "it depends".  I've had up to 600MB in dentry
and inode slabs on a 1GiB machine after updatedb.  This machine
currently has 13MB in dentries, which seems to be reasonable for my
purposes.

Jörn

-- 
Audacity augments courage; hesitation, fear.
-- Publilius Syrus
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