Re: [RFC][DATA] re "ongoing vm suckage"

[Linus Torvalds]

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