On 04/19/2010 01:58 PM, Greg Freemyer wrote:
On Mon, Apr 19, 2010 at 12:30 PM, Eric Sandeen<sandeen@xxxxxxxxxx> wrote:
Greg Freemyer wrote:
Adding Mark Lord in cc.
He wrote a preliminary discard solution last summer. I'm not sure how
it has progressed.
The difference here is that Mark's stuff wasn't as tightly integrated
with the kernel, IIRC. What I saw was more at a user level - make a big
file, map it, discard all the blocks, unlink the file.
It was a good first step, but I think we can do a lot better by using
fs-specific calls to be efficient& targeted about the discards.
Christoph has a similar approach for XFS, FWIW.
-Eric
I haven't looked closely at this patch, but I recall Mark consolidated
numerous discontinuous trim/discard/unmap ranges into a single command
to the SSD drive.
That was why he felt he was getting superior performance. ie. There
was an overhead per command to the drive that was eliminated if a
single more complex command with multiple ranges went to the SSD
drive.
But he's the one that did the work and the benchmarking, so I'll let
him take it from here, especially if I mis-understood what he was
doing.
Greg
This work certainly builds on Mark's early results which clearly showed that
several devices see a win from doing larger/batched discards instead of the fine
grained ones.
Thanks!
Ric
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