On Sat, Apr 04 2009, Arjan van de Ven wrote: > On Sat, 4 Apr 2009 19:22:22 -0400 > Theodore Tso <tytso@xxxxxxx> wrote: > > > > However, the full latency fixes all the writes are synchronous, so it > > must be the case that the delays are caused by the fact that queue is > > getting implicitly unplugged after the synchronous write, and the > > problem is no longer the mixing of WRITE and WRITE_SYNC requests as > > posted in the commit log for 78f707bf. If we remove the automatic > > unplug for WRITE_SYNC requests, and add an explicit unplug where it is > > needed, that should fix the performance regression for this particular > > sqlite test case. > > removing the unplug is bound to be bad; after all we're waiting on the > IO. But maybe it should be "make the unplug a REALLY short time". > At least for rotating storage. For non-rotating .. I'd never wait. Well, either you are submitting a single piece of IO (in which case you just want to unplug or directly submit as part of the submit_bio()), or you are submitting several IOS (in which case you just want to unplug at the end of the IO submission, before waiting). -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
