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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 18 Sep 2007 22:31:07 +1000
From:	David Chinner <dgc@....com>
To:	Mel Gorman <mel@...net.ie>
Cc:	Christoph Lameter <clameter@....com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Goswin von Brederlow <brederlo@...ormatik.uni-tuebingen.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Joern Engel <joern@...fs.org>, andrea@...e.de,
	torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
	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 Tue, Sep 18, 2007 at 11:00:40AM +0100, Mel Gorman wrote:
> We still lack data on what sort of workloads really benefit from large
> blocks (assuming there are any that cannot also be solved by improving
> order-0).

No we don't. All workloads benefit from larger block sizes when
you've got a btree tracking 20 million inodes and a create has to
search that tree for a free inode.  The tree gets much wider and
hence we take fewer disk seeks to traverse the tree. Same for large
directories, btree's tracking free space, etc - everything goes
faster with a larger filesystem block size because we spent less
time doing metadata I/O.

And the other advantage is that sequential I/O speeds also tend to
increase with larger block sizes. e.g. XFS on an Altix (16k pages)
using 16k block size is about 20-25% faster on writes than 4k block
size. See the graphs at the top of page 12:

http://oss.sgi.com/projects/xfs/papers/ols2006/ols-2006-paper.pdf

The benefits are really about scalability and with terabyte sized
disks on the market.....

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/