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Subject[PATCH 0/3 v2] Configurable max discard size
Date
Hi,

Most drivers use UINT_MAX (or some variant thereof) for max discard
size, since they don't have a real limit for a non-data transferring
command. This is fine from a throughput point of view, but for a lot
of devices (all?), it truly sucks on latency. We've seen cases of
hundreds of msec in latencies for reads/writes when deleting files
on an fs with discard enabled. For the problematic devices that we
have tested, artificially limiting the size of the discards issued
brings it down to a more manageable 1-2ms max latencies.

Changes since v1:

- Keep separate sysfs files for hw and sw max discard values.

- Add patch 3, defaulting to 64MB discard sizes.

--
Jens Axboe




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