The current log space reservation code allows multiple wakeups of the
same sleeping waiter to happen. This is a just a waste of cpu time as
well as increasing spin lock hold time. So a new XLOG_TIC_WAKING flag is
added to track if a task is being waken up and skip the wake_up_process()
call if the flag is set.
Running the AIM7 fserver workload on a 2-socket 24-core 48-thread
Broadwell system with a small xfs filesystem on ramfs, the performance
increased from 91,486 jobs/min to 192,666 jobs/min with this change.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
fs/xfs/xfs_log.c | 9 +++++++++
fs/xfs/xfs_log_priv.h | 1 +
2 files changed, 10 insertions(+)
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index c3b610b687d1..ac1dc8db7112 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -232,8 +232,16 @@ xlog_grant_head_wake(
return false;
*free_bytes -= need_bytes;
+
+ /*
+ * Skip task that is being waken up already.
+ */
+ if (tic->t_flags & XLOG_TIC_WAKING)
+ continue;
+
trace_xfs_log_grant_wake_up(log, tic);
wake_up_process(tic->t_task);
+ tic->t_flags |= XLOG_TIC_WAKING;
}
return true;
@@ -264,6 +272,7 @@ xlog_grant_head_wait(
trace_xfs_log_grant_wake(log, tic);
spin_lock(&head->lock);
+ tic->t_flags &= ~XLOG_TIC_WAKING;
if (XLOG_FORCED_SHUTDOWN(log))
goto shutdown;
} while (xlog_space_left(log, &head->grant) < need_bytes);
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index b5f82cb36202..738df09bf352 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -59,6 +59,7 @@ static inline uint xlog_get_client_id(__be32 i)
*/
#define XLOG_TIC_INITED 0x1 /* has been initialized */
#define XLOG_TIC_PERM_RESERV 0x2 /* permanent reservation */
+#define XLOG_TIC_WAKING 0x4 /* task is being waken up */
#define XLOG_TIC_FLAGS \
{ XLOG_TIC_INITED, "XLOG_TIC_INITED" }, \
--
2.18.0
