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Date: Fri, 3 Aug 2001 20:35:14 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Rik van Riel <riel@conectiva.com.br>
cc: Daniel Phillips <phillips@bonn-fries.net>, Ben LaHaise <bcrl@redhat.com>,
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Subject: Re: [RFC][DATA] re "ongoing vm suckage"
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On Sat, 4 Aug 2001, Rik van Riel wrote:
> On Fri, 3 Aug 2001, Linus Torvalds wrote:
>
> > Please just remove the code instead. I don't think it buys you anything.
>
> IIRC you applied the patch introducing that logic because it
> gave a 25% performance increase under some write intensive
> loads (or something like that).

That's the batching code, which is somewhat intertwined with the same
code.

The batching code is a separate issue: when we free the requests, we don't
actually make them available as they get free'd (because then the waiters
will trickle out new requests one at a time and cannot do any merging
etc).

Also, the throttling code probably _did_ make behaviour nicer back when
"sync()" used to use ll_rw_block().  Of course, now most of the IO layer
actually uses "submit_bh()" and bypasses this code completely, so only the
ones that still use it get hit by the unfairness. What a double whammy ;)

		Linus