On Tue, Jan 5, 2021 at 12:49 AM J . Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Mon, Dec 28, 2020 at 07:03:44PM +0200, Amir Goldstein wrote: > > Collect some nfsd stats per export in addition to the global stats. > > Seems like a reasonable thing to do. > > > A new nfsdfs export_stats file is created. It uses the same ops as the > > exports file to iterate the export entries and we use the file's name to > > determine the reported info per export. For example: > > > > $ cat /proc/fs/nfsd/export_stats > > # Version 1.1 > > # Path Client Start-time > > # Stats > > /test localhost 92 > > fh_stale: 0 > > io_read: 9 > > io_write: 1 > > > > Every export entry reports the start time when stats collection > > started, so stats collecting scripts can know if stats where reset > > between samples. > > Yes, you expect svc_export to be created (or destroyed) when a > filesystem is exported (or unexported), or when nfsd starts (or stops). > > But actually it's just a cache entry and can be removed and recreated at > any time. Not much we can do about losing statistics when that happens, > but the start time at least gives us some hope of interpreting the > statistics. > > Why weren't there existing file system statistics that would do the job > in your case? > I am not sure what you mean. We want to know the amount of read/write io for a specific export on the server, including io to/from page cache, which isn't counted by stats of most local filesystems. Unrelated, in our search for those statistics, we were surprised (good surprises) to learn about s_op->show_stats(), but also surprised (bad surprise) to learn how few filesystems implement this method. Thanks, Amir.
