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Date: Sun, 31 Dec 2000 09:12:21 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Alexander Viro <viro@math.psu.edu>
cc: Andrea Arcangeli <andrea@suse.de>, Roman Zippel <zippel@fh-brandenburg.de>,
        "Eric W. Biederman" <ebiederman@uswest.net>,
        Daniel Phillips <phillips@innominate.de>, linux-kernel@vger.kernel.org
Subject: Re: [RFC] Generic deferred file writing
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On Sun, 31 Dec 2000, Alexander Viro wrote:
> 
> On Sun, 31 Dec 2000, Linus Torvalds wrote:
> 
> > The other thing is that one of the common cases for writing is consecutive
> > writing to the end of the file. Now, you figure it out: if get_block()
> > really is a bottle-neck, why not cache the last tree lookup? You'd get a
> > 99% hitrate for that common case.
> 
> Because it is not a bottleneck. The _real_ bottleneck is in ext2_new_block().
> Try to profile it and you'll see.
> 
> We could diddle with ext2_get_block(). No arguments. But the real source of
> PITA is balloc.c, not inode.c. Look at the group descriptor cache code and
> weep. That, and bitmaps handling.

I'm not surprised. Just doign pre-allocation 32 blocks at a time would
probably help. But that code really should be re-written, I think.

		Linus

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