NeilBrown 8d92890bd6 mm/writeback: discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead ... After an NFS page has been written it is considered "unstable" until a COMMIT request succeeds. If the COMMIT fails, the page will be re-written. These "unstable" pages are currently accounted as "reclaimable", either in WB_RECLAIMABLE, or in NR_UNSTABLE_NFS which is included in a 'reclaimable' count. This might have made sense when sending the COMMIT required a separate action by the VFS/MM (e.g. releasepage() used to send a COMMIT). However now that all writes generated by ->writepages() will automatically be followed by a COMMIT (since commit 919e3bd9a8 ("NFS: Ensure we commit after writeback is complete")) it makes more sense to treat them as writeback pages. So this patch removes NR_UNSTABLE_NFS and accounts unstable pages in NR_WRITEBACK and WB_WRITEBACK. A particular effect of this change is that when wb_check_background_flush() calls wb_over_bg_threshold(), the latter will report 'true' a lot less often as the 'unstable' pages are no longer considered 'dirty' (as there is nothing that writeback can do about them anyway). Currently wb_check_background_flush() will trigger writeback to NFS even when there are relatively few dirty pages (if there are lots of unstable pages), this can result in small writes going to the server (10s of Kilobytes rather than a Megabyte) which hurts throughput. With this patch, there are fewer writes which are each larger on average. Where the NR_UNSTABLE_NFS count was included in statistics virtual-files, the entry is retained, but the value is hard-coded as zero. static trace points and warning printks which mentioned this counter no longer report it. [akpm@linux-foundation.org: re-layout comment] [akpm@linux-foundation.org: fix printk warning] Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: Trond Myklebust <trond.myklebust@hammerspace.com> Acked-by: Michal Hocko <mhocko@suse.com> [mm] Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Link: http://lkml.kernel.org/r/87d06j7gqa.fsf@notabene.neil.brown.name Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2020-06-02 10:59:08 -07:00
..
events	mm/writeback: discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead	2020-06-02 10:59:08 -07:00
bpf_probe.h	bpf: Reliably preserve btf_trace_xxx types	2020-03-02 16:49:55 -08:00
define_trace.h
perf.h
syscall.h
trace_events.h	Tracing updates:	2020-02-06 07:12:11 +00:00