On Thu, Nov 28, 2019 at 08:46:57AM +0100, Andrea Vai wrote: > Il giorno mer, 27/11/2019 alle 08.14 +0000, Schmid, Carsten ha > scritto: > > > > > > > Then I started another set of 100 trials and let them run > > tonight, and > > > > the first 10 trials were around 1000s, then gradually decreased > > to > > > > ~300s, and finally settled around 200s with some trials below > > 70-80s. > > > > This to say, times are extremely variable and for the first time > > I > > > > noticed a sort of "performance increase" with time. > > > > > > > > > > The sheer volume of testing (probably some terabytes by now) would > > > exercise the wear leveling algorithm in the FTL. > > > > > But with "old kernel" the copy operation still is "fast", as far as > > i understood. > > If FTL (e.g. wear leveling) would slow down, we would see that also > > in > > the old kernel, right? > > > > Andrea, can you confirm that the same device used with the old fast > > kernel is still fast today? > > Yes, it is still fast. Just ran a 100 trials test and got an average > of 70 seconds with standard deviation = 6 seconds, aligned with the > past values of the same kernel. Then can you collect trace on the old kernel via the previous script? #!/bin/sh MAJ=$1 MIN=$2 MAJ=$(( $MAJ << 20 )) DEV=$(( $MAJ | $MIN )) /usr/share/bcc/tools/trace -t -C \ 't:block:block_rq_issue (args->dev == '$DEV') "%s %d %d", args->rwbs, args->sector, args->nr_sector' \ 't:block:block_rq_insert (args->dev == '$DEV') "%s %d %d", args->rwbs, args->sector, args->nr_sector' Both the two trace points and bcc should be available on the old kernel. Thanks, Ming