On 05/04/2020 09:26, Goffredo Baroncelli wrote: ... > I considered the following scenarios: > - btrfs over ssd > - btrfs over ssd + hdd with my patch enabled > - btrfs over bcache over hdd+ssd > - btrfs over hdd (very, very slow....) > - ext4 over ssd > - ext4 over hdd > > The test machine was an "AMD A6-6400K" with 4GB of ram, where 3GB was used > as cache/buff. > > Data analysis: > > Of course btrfs is slower than ext4 when a lot of sync/flush are involved. Using > apt on a rotational was a dramatic experience. And IMHO this should be replaced > by using the btrfs snapshot capabilities. But this is another (not easy) story. > > Unsurprising bcache performs better than my patch. But this is an expected > result because it can cache also the data chunk (the read can goes directly to > the ssd). bcache perform about +60% slower when there are a lot of sync/flush > and only +20% in the other case. > > Regarding the test with force-unsafe-io (fewer sync/flush), my patch reduce the > time from +256% to +113% than the hdd-only . Which I consider a good > results considering how small is the patch. > > > Raw data: > The data below is the "real" time (as return by the time command) consumed by > apt > > > Test description real (mmm:ss) Delta % > -------------------- ------------- ------- > btrfs hdd w/sync 142:38 +533% > btrfs ssd+hdd w/sync 81:04 +260% > ext4 hdd w/sync 52:39 +134% > btrfs bcache w/sync 35:59 +60% > btrfs ssd w/sync 22:31 reference > ext4 ssd w/sync 12:19 -45% Interesting data but it seems to be missing the case of btrfs ssd+hdd w/sync without your patch in order to tell what difference your patch made. Or am I confused?
