Does this have anything to do with the bug I've reported about 2.4.x
slowing down i/o after heavy sequencial read-only from >=50 files
concurrently? (see BUG raid subsys)
roy
On Mon, 17 Dec 2001, Ingo Molnar wrote:
>
> the attached patch (against 2.5.1-final) includes the next round of RAID-1
> improvements. First it completes the raid1.c cleanups i planned, and it
> also adds a number of new RAID-1 performance features.
>
> Changelog:
>
> - cleaned up the resync engine. It got much simpler and easier to
> maintain, while still saturating the disks. Resync doesnt get stuck
> under heavy load anymore. (this code can be switched to use explicit IO
> barrier requests in the future.)
>
> - rewrote the read balancing code to use three estimators: a per-array
> 'next expected sequential IO' position, plus an IRQ-driven 'estimated
> disk head' position. The head position is now updated from all the IO
> completion routines: end of READ, end of WRITE, end of resync-READ, end
> of resync-WRITE. I've added per-disk tracking of pending requests,
> and the read balancer now detects idle disks and utilizes them before
> trying to read-balance between busy disks. I've also removed the
> sector_count limit that artificially switched the current disk. These
> changes make read balancing more accurate and more effective.
>
> - the old raid1 code used to have a limitation: it has always read from
> the first disk until the resync finished. Now the code will
> read-balance READ requests up to the resync boundary. This should
> further improve performance during resyncs.
>
> - added the 'idle IO resync' feature which we used to have in the 2.2
> patches, but via a different implementation that does not touch the
> generic block IO code. Resync happens only when there is no normal IO
> pending on the array. This feature should make resync a more seemless
> operation. Resync behavior can be tuned via the speed_limit_min and
> speed_limit_max sysctl tunables. Default for the minimum resync speed
> is 500 KB/sec, the maximum is 200 MB/sec.
>
> - fixed a number of sector_t <=> unsigned long bugs still left.
>
> despite these new features added, the patch makes raid1.c 8% smaller, so
> it's a win-win situation :-) I've tested the patch on UP and SMP as well,
> and it's working just fine for me both in degraded-mode and normal mode,
> but the usual warnings (do not use on production system, etc.) apply.
>
> Comments, reports, suggestions welcome,
>
> Ingo
>
-- Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCAComputers are like air conditioners. They stop working when you open Windows.
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This archive was generated by hypermail 2b29 : Sun Dec 23 2001 - 21:00:16 EST