On Tue, Jan 12, 2021 at 11:36:14PM +0800, kernel test robot wrote: > > Greeting, > > FYI, we noticed a -18.3% regression of fio.write_iops due to commit: > > > commit: e076ab2a2ca70a0270232067cd49f76cd92efe64 ("btrfs: shrink delalloc > pages instead of full inodes") > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > > in testcase: fio-basic > on test machine: 192 threads Intel(R) Xeon(R) CPU @ 2.20GHz with 192G memory > with following parameters: > > disk: 1SSD > fs: btrfs > runtime: 300s > nr_task: 8 > rw: randwrite > bs: 4k > ioengine: sync > test_size: 256g
Though I do a similar test (emulating bit torrent workload), it's a bit extreme as it's 4k synchronous on a huge file. It always takes a lot of time but could point out some concurrency issues namely on faster devices. There are 8 threads possibly competing for the same inode lock or other locks related to it. The mentioned commit fixed another perf regression on a much more common workload (untgrring files), so at this point drop in this fio workload is inevitable.