On 10/31/2016 05:14 PM, Christoph Hellwig wrote:
On Fri, Oct 28, 2016 at 01:11:55PM +0300, Avi Kivity wrote:
With these patches, is it reasonable to run with discard enabled, or is
more work needed?
As usual the answer is: it depends. With the high-end NVMe devices
I've been testing with you absolutely should enable discard. With
SAS SSDs the same is probably true. I haven't done much testing with
SATA SSDs but I'd be more cautious there, especially as very few seem
to support queued TRIM yet.
Thanks.
The big problem with "it depends" is that usually the information it
depends on is not available, so the application has to rely on a human
to guess correctly. With the trend for machines to be managed by
machines, it's really hard to get optimal performance. So exposure of
any information that can help to make a decision, including that the
kernel can make good use of TRIM, will be very helpful.
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