Quoting Bernd Schubert (2013-05-24 04:35:37) > Hello Chris, > > On 05/23/2013 10:33 PM, Chris Mason wrote: > > But I was using 8 drives. I'll try with 12. > >> > > My benchmarks were on flash, so the rmw I was seeing may not have had as > > big an impact. > > > I just further played with it and simply introduced a requeue in > raid56_rmw_stripe() if the rbio is 'younger' than 50 jiffies. I can > still see reads, but by a factor 10 lower than before. And this is > sufficient to bring performance almost to that of direc-io. > This is certainly no upstream code, I hope I find some time over the > weekend to come up with something better. Interesting. This probably shows that we need to do a better job of maintaining a plug across the writepages calls, or that we need to be much more aggressive in writepages to add more pages once we've started. > > Btw, I also noticed the cache logic copies pages from those rmw-threads. > Well, this a numa system and memory bandwith is terribly bad from the > remote cpu. These worker threads probably should numa aware and only > handle rbios from their own cpu. Yes, all of the helpers (especially crc and parity) should be made numa aware. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
