Am Donnerstag, 7. Februar 2019, 11:27:50 schrieb Jan Kara: > On Fri 01-02-19 09:19:04, Dave Chinner wrote: > > Maybe for memcgs, but that's exactly the oppose of what we want to > > do for global caches (e.g. filesystem metadata caches). We need to > > make sure that a single, heavily pressured cache doesn't evict small > > caches that lower pressure but are equally important for > > performance. > > > > e.g. I've noticed recently a significant increase in RMW cycles in > > XFS inode cache writeback during various benchmarks. It hasn't > > affected performance because the machine has IO and CPU to burn, but > > on slower machines and storage, it will have a major impact. > > Just as a data point, our performance testing infrastructure has bisected > down to the commits discussed in this thread as the cause of about 40% > regression in XFS file delete performance in bonnie++ benchmark. We also bisected our big IO-performance problem of an imap-server (starting with 4.19.3) down to mm: don't reclaim inodes with many attached pages commit a76cf1a474d7dbcd9336b5f5afb0162baa142cf0 upstream. On other servers the filesystems sometimes seems to hang for 10 seconds and more. We also see a performance regression compared to 4.14 even with this patch reverted, but much less dramatic. Now I saw this thread and I'll try to revert 172b06c32b949759fe6313abec514bc4f15014f4 and see if this helps. Regards, -- Wolfgang Walter Studentenwerk München Anstalt des öffentlichen Rechts
