On 2011-01-25 11:21, Tejun Heo wrote: > Hello, Darrick. > > On Mon, Jan 24, 2011 at 12:31:55PM -0800, Darrick J. Wong wrote: >>> So, I think it's better to start with something simple and improve it >>> with actual testing. If the current simple implementation can match >>> Darrick's previous numbers, let's first settle the mechanisms. We can >> >> Yep, the fsync-happy numbers more or less match... at least for 2.6.37: >> http://tinyurl.com/4q2xeao > > Good to hear. Thanks for the detailed testing. > >> I'll give 2.6.38-rc2 a try later, though -rc1 didn't boot for me, so these >> numbers are based on a backport to .37. :( > > Well, there hasn' been any change in the area during the merge window > anyway, so I think testing on 2.6.37 should be fine. > >>> I don't really think we should design the whole thing around broken >>> devices which incorrectly report writeback cache when it need not. >>> The correct place to work around that is during device identification >>> not in the flush logic. >> >> elm3a4_sas and elm3c71_extsas advertise writeback cache yet the >> flush completion times are suspiciously low. I suppose it could be >> useful to disable flushes to squeeze out that last bit of >> performance, though I don't know how one goes about querying the >> disk array to learn if there's a battery behind the cache. I guess >> the current mechanism (admin knob that picks a safe default) is good >> enough. > > Yeap, that or a blacklist of devices which lie. > > Jens, what do you think? If you don't object, let's put this through > linux-next. I like the approach, I'll queue it up for 2.6.39. -- 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
