On Tue, 17 Aug 2021 at 11:32, Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> wrote: > > * Miklos Szeredi (miklos@xxxxxxxxxx) wrote: > > On Tue, 17 Aug 2021 at 04:22, Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx> wrote: > > > > > > This patchset adds support of per-file DAX for virtiofs, which is > > > inspired by Ira Weiny's work on ext4[1] and xfs[2]. > > > > Can you please explain the background of this change in detail? > > > > Why would an admin want to enable DAX for a particular virtiofs file > > and not for others? > > Where we're contending on virtiofs dax cache size it makes a lot of > sense; it's quite expensive for us to map something into the cache > (especially if we push something else out), so selectively DAXing files > that are expected to be hot could help reduce cache churn. If this is a performance issue, it should be fixed in a way that doesn't require hand tuning like you suggest, I think. I'm not sure what the ext4/xfs case for per-file DAX is. Maybe that can help understand the virtiofs case as well. Thanks, Miklos
