Messages in this thread | | | From | Jens Axboe <> | Subject | [PATCH 0/3 v2] Configurable max discard size | Date | Tue, 14 Jul 2015 12:48:20 -0600 |
| |
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
| |