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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
