[PATCH 04/24] netfs: Record contention stats for writeback lock
From: David Howells <dhowells@redhat.com>
Date: 2024-07-29 16:20:53
Also in:
ceph-devel, linux-cifs, linux-fsdevel, linux-mm, linux-nfs, lkml, netfs, v9fs
Subsystem:
filesystems (vfs and infrastructure), filesystems [netfs library], the rest · Maintainers:
Alexander Viro, Christian Brauner, David Howells, Paulo Alcantara, Linus Torvalds
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: David 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 --- fs/netfs/internal.h | 2 ++ fs/netfs/stats.c | 5 +++++ fs/netfs/write_issue.c | 10 +++++++--- 3 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index 7773f3d855a9..9e6e0e59d7e4 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h@@ -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);
diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
index 95ed2d2623a8..5fe1c396e24f 100644
--- a/fs/netfs/stats.c
+++ b/fs/netfs/stats.c@@ -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);
diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c
index 9258d30cffe3..e7d4f39b8fdc 100644
--- a/fs/netfs/write_issue.c
+++ b/fs/netfs/write_issue.c@@ -503,10 +503,14 @@ int netfs_writepages(struct address_space *mapping, struct folio *folio; int error = 0; - if (wbc->sync_mode == WB_SYNC_ALL) + 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); - else if (!mutex_trylock(&ictx->wb_lock)) - return 0; + } /* Need the first folio to be able to set up the op. */ folio = writeback_iter(mapping, wbc, NULL, &error);