[XFS] Per iclog callback chain lock
Rather than use the icloglock for protecting the iclog completion callback
chain, use a new per-iclog lock so that walking the callback chain doesn't
require holding a global lock.
This reduces contention on the icloglock during transaction commit and log
I/O completion by reducing the number of times we need to hold the global
icloglock during these operations.
SGI-PV: 978729
SGI-Modid: xfs-linux-melb:xfs-kern:30770a
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 01c63db..104b623 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -324,6 +324,19 @@
* - ic_offset is the current number of bytes written to in this iclog.
* - ic_refcnt is bumped when someone is writing to the log.
* - ic_state is the state of the iclog.
+ *
+ * Because of cacheline contention on large machines, we need to separate
+ * various resources onto different cachelines. To start with, make the
+ * structure cacheline aligned. The following fields can be contended on
+ * by independent processes:
+ *
+ * - ic_callback_*
+ * - ic_refcnt
+ * - fields protected by the global l_icloglock
+ *
+ * so we need to ensure that these fields are located in separate cachelines.
+ * We'll put all the read-only and l_icloglock fields in the first cacheline,
+ * and move everything else out to subsequent cachelines.
*/
typedef struct xlog_iclog_fields {
sv_t ic_forcesema;
@@ -332,18 +345,23 @@
struct xlog_in_core *ic_prev;
struct xfs_buf *ic_bp;
struct log *ic_log;
- xfs_log_callback_t *ic_callback;
- xfs_log_callback_t **ic_callback_tail;
-#ifdef XFS_LOG_TRACE
- struct ktrace *ic_trace;
-#endif
int ic_size;
int ic_offset;
- atomic_t ic_refcnt;
int ic_bwritecnt;
ushort_t ic_state;
char *ic_datap; /* pointer to iclog data */
-} xlog_iclog_fields_t;
+#ifdef XFS_LOG_TRACE
+ struct ktrace *ic_trace;
+#endif
+
+ /* Callback structures need their own cacheline */
+ spinlock_t ic_callback_lock ____cacheline_aligned_in_smp;
+ xfs_log_callback_t *ic_callback;
+ xfs_log_callback_t **ic_callback_tail;
+
+ /* reference counts need their own cacheline */
+ atomic_t ic_refcnt ____cacheline_aligned_in_smp;
+} xlog_iclog_fields_t ____cacheline_aligned_in_smp;
typedef union xlog_in_core2 {
xlog_rec_header_t hic_header;
@@ -366,6 +384,7 @@
#define ic_bp hic_fields.ic_bp
#define ic_log hic_fields.ic_log
#define ic_callback hic_fields.ic_callback
+#define ic_callback_lock hic_fields.ic_callback_lock
#define ic_callback_tail hic_fields.ic_callback_tail
#define ic_trace hic_fields.ic_trace
#define ic_size hic_fields.ic_size
