On Sat, 4 Apr 2009, Jens Axboe wrote: > > > > I'm sorry, but that fsync thing _is_ a real-world case, and it's the one > > that a hell of a lot more people care about than some idiotic sqlite > > throughput issue. > > sqlite is just one case, I'm sure there are others. My point is that we > should make sure that we don't regress on the throughput side. It's a > trade off, we don't want throughput to fall through the floor either. Jens, we _have_ regressed on the latency side. Everybody agrees. Also, I may be odd, but I really do think latency is more important than throughput. When my disk has latencies in the sub-milliseconds, I simply do not think it is _acceptable_ to have hickups that affect my workload in human-visible terms. You say sqlite might regress by 4-5x. But Ted's numbers improve latencies by mor than that. I haven't re-created them yet myself (still reading email), but the point is, 4-5x may sound bad to you, but turn it around: the current latency situation is _really_ bad. If we can fix it, we definitely should. > > Quite frankly, the fact that I can see _seconds_ of latencies with a > > really good SSD is not acceptable. The fact that it is by design is even > > less so. > > Agree, multi-second latencies is not acceptable. I can literally send you strace output from my MUA, where it pauses for ten seconds after it has written about 5kB (that's _kilobytes_) of data and does a 'fsync'. That's the load that Ted worked on and has a solution for. Linus -- 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
