Unverified Commit ef966d73 authored by David Howells's avatar David Howells Committed by Christian Brauner
Browse files

netfs: Record contention stats for writeback lock 



Record statistics for contention upon the writeback serialisation lock that
prevents racing writeback calls from causing each other to interleave their
writebacks.  These can be viewed in /proc/fs/netfs/stats on the WbLock line,
with skip=N indicating the number of non-SYNC writebacks skipped and wait=N
indicating the number of SYNC writebacks that waited.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: Steve French <sfrench@samba.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20240814203850.2240469-5-dhowells@redhat.com/

 # v2
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 43ebbf93

fs/netfs/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -117,6 +117,8 @@ extern atomic_t netfs_n_wh_upload_failed; 
extern atomic_t netfs_n_wh_write;

extern atomic_t netfs_n_wh_write_done;

extern atomic_t netfs_n_wh_write_failed;

extern atomic_t netfs_n_wb_lock_skip;

extern atomic_t netfs_n_wb_lock_wait;



int netfs_stats_show(struct seq_file *m, void *v);

fs/netfs/stats.c

+5 −0
Original line number Diff line number Diff line
@@ -39,6 +39,8 @@ atomic_t netfs_n_wh_upload_failed; 
atomic_t netfs_n_wh_write;

atomic_t netfs_n_wh_write_done;

atomic_t netfs_n_wh_write_failed;

atomic_t netfs_n_wb_lock_skip;

atomic_t netfs_n_wb_lock_wait;



int netfs_stats_show(struct seq_file *m, void *v)

{
@@ -78,6 +80,9 @@ int netfs_stats_show(struct seq_file *m, void *v) 
		   atomic_read(&netfs_n_rh_rreq),

		   atomic_read(&netfs_n_rh_sreq),

		   atomic_read(&netfs_n_wh_wstream_conflict));

	seq_printf(m, "WbLock : skip=%u wait=%u\n",

		   atomic_read(&netfs_n_wb_lock_skip),

		   atomic_read(&netfs_n_wb_lock_wait));

	return fscache_stats_show(m);

}

EXPORT_SYMBOL(netfs_stats_show);

fs/netfs/write_issue.c

+7 −3
Original line number Diff line number Diff line
@@ -505,10 +505,14 @@ int netfs_writepages(struct address_space *mapping, 
	struct folio *folio;

	int error = 0;



	if (wbc->sync_mode == WB_SYNC_ALL)

		mutex_lock(&ictx->wb_lock);

	else if (!mutex_trylock(&ictx->wb_lock))

	if (!mutex_trylock(&ictx->wb_lock)) {

		if (wbc->sync_mode == WB_SYNC_NONE) {

			netfs_stat(&netfs_n_wb_lock_skip);

			return 0;

		}

		netfs_stat(&netfs_n_wb_lock_wait);

		mutex_lock(&ictx->wb_lock);

	}



	/* Need the first folio to be able to set up the op. */

	folio = writeback_iter(mapping, wbc, NULL, &error);