xfs: convert CIL to unordered per cpu lists

So that we can remove the cil_lock which is a global serialisation
point. We've already got ordering sorted, so all we need to do is
treat the CIL list like the busy extent list and reconstruct it
before the push starts.

This is what we're trying to avoid:

 -   75.35%     1.83%  [kernel]            [k] xfs_log_commit_cil
    - 46.35% xfs_log_commit_cil
       - 41.54% _raw_spin_lock
          - 67.30% do_raw_spin_lock
               66.96% __pv_queued_spin_lock_slowpath

Which happens on a 32p system when running a 32-way 'rm -rf'
workload. After this patch:

-   20.90%     3.23%  [kernel]               [k] xfs_log_commit_cil
   - 17.67% xfs_log_commit_cil
      - 6.51% xfs_log_ticket_ungrant
           1.40% xfs_log_space_wake
        2.32% memcpy_erms
      - 2.18% xfs_buf_item_committing
         - 2.12% xfs_buf_item_release
            - 1.03% xfs_buf_unlock
                 0.96% up
              0.72% xfs_buf_rele
        1.33% xfs_inode_item_format
        1.19% down_read
        0.91% up_read
        0.76% xfs_buf_item_format
      - 0.68% kmem_alloc_large
         - 0.67% kmem_alloc
              0.64% __kmalloc
        0.50% xfs_buf_item_size

It kinda looks like the workload is running out of log space all
the time. But all the spinlock contention is gone and the
transaction commit rate has gone from 800k/s to 1.3M/s so the amount
of real work being done has gone up a *lot*.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 563145ea0f7d..f00f11c18116 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -224,6 +224,7 @@ struct xfs_cil_ctx {
 	struct xlog_ticket	*ticket;	/* chkpt ticket */
 	atomic_t		space_used;	/* aggregate size of regions */
 	struct list_head	busy_extents;	/* busy extents in chkpt */
+	struct list_head	log_items;	/* log items in chkpt */
 	struct xfs_log_vec	*lv_chain;	/* logvecs being pushed */
 	struct list_head	iclog_entry;
 	struct list_head	committing;	/* ctx committing list */
@@ -262,8 +263,6 @@ struct xfs_cil {
 	struct xlog		*xc_log;
 	unsigned long		xc_flags;
 	atomic_t		xc_iclog_hdrs;
-	struct list_head	xc_cil;
-	spinlock_t		xc_cil_lock;
 	struct workqueue_struct	*xc_push_wq;
 
 	struct rw_semaphore	xc_ctx_lock ____cacheline_aligned_in_smp;