On 7/19/24 2:13 PM, Petr Vorel wrote: > Hi Jens, all, > >> On 7/19/24 11:43 AM, Petr Vorel wrote: >>> Hi all, > >>> LTP AIO DIO tests aiodio_sparse.c [1] and dio_sparse.c [2] (using [3]) slowed >>> down on kernel 6.6 on Btrfs and XFS, when run with default parameters. These >>> tests create 100 MB sparse file and write zeros (using libaio or O_DIRECT) while >>> 16 other processes reads the buffer and check only zero is there. > >>> Runtime of this particular setup (i.e. 100 MB file) on Btrfs and XFS on the >>> same system slowed down 9x (6.5: ~1 min 6.6: ~9 min). Ext4 is not affected. >>> (Non default parameter creates much smaller file, thus the change is not that >>> obvious). > >>> Because the slowdown has been here for few kernel releases I suppose nobody >>> complained and the test is somehow artificial (nobody uses this in a real world). >>> But still it'd be good to double check the problem. I can bisect a particular >>> commit. > >>> Because 2 filesystems affected, could be "Improve asynchronous iomap DIO >>> performance" [4] block layer change somehow related? > >> No, because that got disabled before release for unrelated reasons. Why >> don't you just bisect it, since you have a simple test case? > > Jens, thanks for info. Sure, I'll bisect next week and report. > > The reason I reported before bisecting is because it wouldn't be the > first time the test was "artificial" and therefore reported problem > was not fixed. If it's a real problem I would expect it would be also > caught by other people or even by fstests. Didn't look at the test cases, so yeah may very well be bogus. But it also may not... And a bisection may help shine some light on that too, outside of just highlighting what commit made it slower. -- Jens Axboe
