[XFS] Reorganise xlog_t for better cacheline isolation of contention

To reduce contention on the log in large CPU count, separate out different
parts of the xlog_t structure onto different cachelines. Move each lock
onto a different cacheline along with all the members that are
accessed/modified while that lock is held.

Also, move the debugging code into debug code.

SGI-PV: 978729
SGI-Modid: xfs-linux-melb:xfs-kern:30772a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

1 files changed, 30 insertions, 25 deletions

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index c1583960009d..8952a392b5f3 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -361,7 +361,7 @@ typedef struct xlog_iclog_fields {
 
         /* reference counts need their own cacheline */
         atomic_t                ic_refcnt ____cacheline_aligned_in_smp;
-} xlog_iclog_fields_t ____cacheline_aligned_in_smp;
+} xlog_iclog_fields_t;
 
 typedef union xlog_in_core2 {
         xlog_rec_header_t       hic_header;
@@ -402,8 +402,29 @@ typedef struct xlog_in_core {
  * that round off problems won't occur when releasing partial reservations.
  */
 typedef struct log {
+        /* The following fields don't need locking */
+        struct xfs_mount        *l_mp;          /* mount point */
+        struct xfs_buf          *l_xbuf;        /* extra buffer for log
+                                                 * wrapping */
+        struct xfs_buftarg      *l_targ;        /* buftarg of log */
+        uint                    l_flags;
+        uint                    l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */
+        struct xfs_buf_cancel   **l_buf_cancel_table;
+        int                     l_iclog_hsize;  /* size of iclog header */
+        int                     l_iclog_heads;  /* # of iclog header sectors */
+        uint                    l_sectbb_log;   /* log2 of sector size in BBs */
+        uint                    l_sectbb_mask;  /* sector size (in BBs)
+                                                 * alignment mask */
+        int                     l_iclog_size;   /* size of log in bytes */
+        int                     l_iclog_size_log; /* log power size of log */
+        int                     l_iclog_bufs;   /* number of iclog buffers */
+        xfs_daddr_t             l_logBBstart;   /* start block of log */
+        int                     l_logsize;      /* size of log in bytes */
+        int                     l_logBBsize;    /* size of log in BB chunks */
+
         /* The following block of fields are changed while holding icloglock */
-        sema_t                  l_flushsema;    /* iclog flushing semaphore */
+        sema_t                  l_flushsema ____cacheline_aligned_in_smp;
+                                                /* iclog flushing semaphore */
         int                     l_flushcnt;     /* # of procs waiting on this
                                                  * sema */
         int                     l_covered_state;/* state of "covering disk
@@ -413,27 +434,14 @@ typedef struct log {
         xfs_lsn_t               l_tail_lsn;     /* lsn of 1st LR with unflushed
                                                  * buffers */
         xfs_lsn_t               l_last_sync_lsn;/* lsn of last LR on disk */
-        struct xfs_mount        *l_mp;          /* mount point */
-        struct xfs_buf          *l_xbuf;        /* extra buffer for log
-                                                 * wrapping */
-        struct xfs_buftarg      *l_targ;        /* buftarg of log */
-        xfs_daddr_t             l_logBBstart;   /* start block of log */
-        int                     l_logsize;      /* size of log in bytes */
-        int                     l_logBBsize;    /* size of log in BB chunks */
         int                     l_curr_cycle;   /* Cycle number of log writes */
         int                     l_prev_cycle;   /* Cycle number before last
                                                  * block increment */
         int                     l_curr_block;   /* current logical log block */
         int                     l_prev_block;   /* previous logical log block */
-        int                     l_iclog_size;   /* size of log in bytes */
-        int                     l_iclog_size_log; /* log power size of log */
-        int                     l_iclog_bufs;   /* number of iclog buffers */
-
-        /* The following field are used for debugging; need to hold icloglock */
-        char                    *l_iclog_bak[XLOG_MAX_ICLOGS];
 
         /* The following block of fields are changed while holding grant_lock */
-        spinlock_t              l_grant_lock;
+        spinlock_t              l_grant_lock ____cacheline_aligned_in_smp;
         xlog_ticket_t           *l_reserve_headq;
         xlog_ticket_t           *l_write_headq;
         int                     l_grant_reserve_cycle;
@@ -441,19 +449,16 @@ typedef struct log {
         int                     l_grant_write_cycle;
         int                     l_grant_write_bytes;
 
-        /* The following fields don't need locking */
 #ifdef XFS_LOG_TRACE
         struct ktrace           *l_trace;
         struct ktrace           *l_grant_trace;
 #endif
-        uint                    l_flags;
-        uint                    l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */
-        struct xfs_buf_cancel   **l_buf_cancel_table;
-        int                     l_iclog_hsize;  /* size of iclog header */
-        int                     l_iclog_heads;  /* # of iclog header sectors */
-        uint                    l_sectbb_log;   /* log2 of sector size in BBs */
-        uint                    l_sectbb_mask;  /* sector size (in BBs)
-                                                 * alignment mask */
+
+        /* The following field are used for debugging; need to hold icloglock */
+#ifdef DEBUG
+        char                    *l_iclog_bak[XLOG_MAX_ICLOGS];
+#endif
+
 } xlog_t;
 
 #define XLOG_FORCED_SHUTDOWN(log)       ((log)->l_flags & XLOG_IO_ERROR)