Re: 2.6.35 Regression: Ages spent discarding blocks that weren'tused!
From: Nigel Cunningham
Date: Wed Aug 04 2010 - 17:22:39 EST
On 04/08/10 22:44, Mark Lord wrote:
Looks to me like more and more things are using the block discard
functionality, and as predicted it is slowing things down enormously.
The problem is that we still only discard tiny bits (a single range
per TRIM command, rather than batching larger ranges and larger numbers
of ranges into single TRIM commands.
That's a very poor implementation, especially when things start enabling
it by default. Eg. the swap code, mke2fs, etc..
I was hoping for a nice quick and simple answer. Since I haven't got
one, I'll try to find time to do a git bisect. I think I'll also look at
the swap code more carefully and see if it's doing the sensible thing. I
can't (at the moment) see the logic behind calling discard when
allocating swap. At freeing time makes much more sense to me.
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