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* [RFC PATCH 0/1] ext4: Try to better reuse recently freed space
@ 2013-07-04  9:11 Lukas Czerner
  2013-07-04  9:11 ` [RFC PATCH 1/1] " Lukas Czerner
  0 siblings, 1 reply; 12+ messages in thread
From: Lukas Czerner @ 2013-07-04  9:11 UTC (permalink / raw)
  To: linux-ext4; +Cc: enwlinux, Jose_Mario_Gallegos, jordan_hargrave, rwheeler

Hi all,

as I just recently discovered here http://www.ogris.de/blkalloc/ ext4 have
some unexpected allocation strategies which can cause some problems in
certain scenarios (see the 1/1 patch).

This is my attempt to fix this, however I think that this will need some
discussion because it changes some of the block allocator heuristic
quite significantly and I would like to make sure that it will not hurt
our performance in some widely used workloads. Eric, could you run your
performance testing with your test suite to see how it performs ?

Also, I think that the old behaviour might be quite helpful for SSD because
we're not overwriting existing blocks but rather trying to use new one, so
the firmware should have easier job. However I do not know how significant
impact if at all it might have. If we find out that this is helpful for
SSD we might make this conditional depending on the type of the device.

Which brings me to the other problem. Since the original behaviour is really
bad for thinly provisioned devices we would like to avoid using it even if
the underlying storage is SSD, however IIRC there is no way to distinguish
this from within the kernel.

See the comparison between the old and new allocator behaviour
http://people.redhat.com/lczerner/allocator/

Comments and testing is welcomed.

Thanks!
-Lukas

^ permalink raw reply	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2013-07-10 12:24 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-07-04  9:11 [RFC PATCH 0/1] ext4: Try to better reuse recently freed space Lukas Czerner
2013-07-04  9:11 ` [RFC PATCH 1/1] " Lukas Czerner
2013-07-04 15:09   ` Jan Kara
2013-07-04 15:32     ` Lukáš Czerner
2013-07-04 16:06       ` Jose_Mario_Gallegos
2013-07-08  7:38       ` [PATCH v2] " Lukas Czerner
2013-07-08  8:56         ` Jan Kara
2013-07-08  9:24           ` Lukáš Czerner
2013-07-08 11:59             ` Jan Kara
2013-07-08 21:27               ` Andreas Dilger
2013-07-10 11:30                 ` Lukáš Czerner
2013-07-10 11:18               ` Lukáš Czerner

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