Re: merging discard request in the block layer

From: Christoph Hellwig
Date: Wed Mar 23 2011 - 09:01:42 EST

On Tue, Mar 22, 2011 at 10:03:57PM +0100, Jens Axboe wrote:
> > That would seem to indicate a bug in the merging logic instead.
> What kind of max discard size does you device have? If the max discard
> size is smaller than the regular request size, this could help.

It's a SCSI device, so the max discard size is a lot larger:

# cat /sys/block/sda/queue/max_sectors_kb
# cat /sys/block/sda/queue/max_hw_sectors_kb
# cat /sys/block/sda/queue/discard_max_bytes

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