James Bottomley wrote:
This means you have to drain the outstanding NCQ commands (stalling the device) before you can send a TRIM. If we do this for every discard, the performance impact will be pretty devastating, hence the need to coalesce. It's nothing really to do with device characteristics, it's an ATA protocol problem.
.. I don't think that's really much of an issue -- we already have to do that for cache-flushes whenever barriers are enabled. Yes it costs, but not too much. The current problem is that the only existing SSDs in the wild with TRIM, take 100s of milliseconds per TRIM, mostly regardless of the amount being TRIMmed. Sure, some TRIMs take only 10-20ms, and very large ones (millions of sectors) can take 1-2 seconds, but most are in the 100ms range. Cheers -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
