From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Chinner <dgc@sgi.com>
Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support)
Date: Thu, 13 Sep 2007 11:49:05 +1000
Message-ID: <20070913014905.GV995458@sgi.com>
References: <20070911060349.993975297@sgi.com> <200709111600.18756.nickpiggin@yahoo.com.au> <20070912014917.GJ995458@sgi.com> <200709120127.33832.nickpiggin@yahoo.com.au>
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Cc: David Chinner <dgc@sgi.com>, Mel Gorman <mel@skynet.ie>,
	Christoph Lameter <clameter@sgi.com>, andrea@suse.de,
	torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	William Lee Irwin III <wli@holomorphy.com>,
	Jens Axboe <jens.axboe@oracle.com>,
	Badari Pulavarty <pbadari@gmail.com>,
	Maxim Levitsky <maximlevitsky@gmail.com>,
	Fengguang Wu <fengguang.wu@gmail.com>,
	swin wang <wangswin@gmail.com>, totty.lu@gmail.com,
	hugh@veritas.com, joern@lazybastard.org
To: Nick Piggin <nickpiggin@yahoo.com.au>
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On Wed, Sep 12, 2007 at 01:27:33AM +1000, Nick Piggin wrote:
> > IOWs, we already play these vmap harm-minimisation games in the places
> > where we can, but still the overhead is high and something we'd prefer
> > to be able to avoid.
> 
> I don't think you've looked nearly far enough with all this low hanging
> fruit.

Ok, so we need to hack the vm to optimise it further. When it comes to
TLB flush code and optimising that sort of stuff, I'm out of my depth.

> I just gave 4 things which combined might easily reduce xfs vmap overhead
> by several orders of magnitude, all without changing much code at all.

Patches would be greatly appreciately. You obviously understand this
vm code much better than I do, so if it's easy to fix by adding some
generic vmap cache thingy, please do.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group