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3815832a2a
linux-next/fs/xfs
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Dave Chinner 3815832a2a xfs: Don't allocate new buffers on every call to _xfs_buf_find 
Stats show that for an 8-way unlink @ ~80,000 unlinks/s we are doing
~1 million cache hit lookups to ~3000 buffer creates. That's almost
3 orders of magnitude more cahce hits than misses, so optimising for
cache hits is quite important. In the cache hit case, we do not need
to allocate a new buffer in case of a cache miss, so we are
effectively hitting the allocator for no good reason for vast the
majority of calls to _xfs_buf_find. 8-way create workloads are
showing similar cache hit/miss ratios.

The result is profiles that look like this:

     samples  pcnt function                        DSO
     _______ _____ _______________________________ _________________

     1036.00 10.0% _xfs_buf_find                   [kernel.kallsyms]
      582.00  5.6% kmem_cache_alloc                [kernel.kallsyms]
      519.00  5.0% __memcpy                        [kernel.kallsyms]
      468.00  4.5% __ticket_spin_lock              [kernel.kallsyms]
      388.00  3.7% kmem_cache_free                 [kernel.kallsyms]
      331.00  3.2% xfs_log_commit_cil              [kernel.kallsyms]


Further, there is a fair bit of work involved in initialising a new
buffer once a cache miss has occurred and we currently do that under
the rbtree spinlock. That increases spinlock hold time on what are
heavily used trees.

To fix this, remove the initialisation of the buffer from
_xfs_buf_find() and only allocate the new buffer once we've had a
cache miss. Initialise the buffer immediately after allocating it in
xfs_buf_get, too, so that is it ready for insert if we get another
cache miss after allocation. This minimises lock hold time and
avoids unnecessary allocator churn. The resulting profiles look
like:

     samples  pcnt function                    DSO
     _______ _____ ___________________________ _________________

     8111.00  9.1% _xfs_buf_find               [kernel.kallsyms]
     4380.00  4.9% __memcpy                    [kernel.kallsyms]
     4341.00  4.8% __ticket_spin_lock          [kernel.kallsyms]
     3401.00  3.8% kmem_cache_alloc            [kernel.kallsyms]
     2856.00  3.2% xfs_log_commit_cil          [kernel.kallsyms]
     2625.00  2.9% __kmalloc                   [kernel.kallsyms]
     2380.00  2.7% kfree                       [kernel.kallsyms]
     2016.00  2.3% kmem_cache_free             [kernel.kallsyms]

Showing a significant reduction in time spent doing allocation and
freeing from slabs (kmem_cache_alloc and kmem_cache_free).

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
2011-10-11 21:15:08 -05:00
..
Kconfig quota: Make QUOTACTL config be selected by its users 2010-10-05 12:16:37 +02:00
kmem.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
kmem.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
Makefile xfs: fix tracing builds inside the source tree 2011-08-22 16:37:24 -05:00
mrlock.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
time.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
uuid.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
uuid.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_acl.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_acl.h xfs: Fix build breakage in xfs_iops.c when CONFIG_FS_POSIX_ACL is not set 2011-08-01 02:35:04 -04:00
xfs_ag.h xfs: Remove the macro XFS_BUF_PTR 2011-07-25 15:03:13 -05:00
xfs_alloc_btree.c xfs: remove leftovers of the old btree tracing code 2011-07-13 13:43:50 +02:00
xfs_alloc_btree.h
xfs_alloc.c xfs: Remove the macro XFS_BUF_ERROR and family 2011-07-25 14:57:46 -05:00
xfs_alloc.h xfs: do not discard alloc btree blocks 2011-05-24 11:17:22 -05:00
xfs_aops.c xfs: introduce xfs_bmapi_read() 2011-10-11 21:15:03 -05:00
xfs_aops.h xfs: remove i_iocount 2011-10-11 21:15:01 -05:00
xfs_attr_leaf.c xfs: introduce xfs_bmapi_read() 2011-10-11 21:15:03 -05:00
xfs_attr_leaf.h
xfs_attr_sf.h
xfs_attr.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_attr.h
xfs_bit.c
xfs_bit.h
xfs_bmap_btree.c xfs: remove leftovers of the old btree tracing code 2011-07-13 13:43:50 +02:00
xfs_bmap_btree.h
xfs_bmap.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_bmap.h xfs: cleanup xfs_bmap.h 2011-10-11 21:15:07 -05:00
xfs_btree.c xfs: Check the return value of xfs_trans_get_buf() 2011-10-11 21:15:01 -05:00
xfs_btree.h xfs: Remove the macro XFS_BUF_PTR 2011-07-25 15:03:13 -05:00
xfs_buf_item.c xfs: call xfs_buf_delwri_queue directly 2011-10-11 21:14:59 -05:00
xfs_buf_item.h xfs: use struct list_head for the buf cancel table 2010-12-16 16:05:22 -06:00
xfs_buf.c xfs: Don't allocate new buffers on every call to _xfs_buf_find 2011-10-11 21:15:08 -05:00
xfs_buf.h xfs: use the "delwri" terminology consistently 2011-10-11 21:15:00 -05:00
xfs_da_btree.c xfs: rename xfs_bmapi to xfs_bmapi_write 2011-10-11 21:15:04 -05:00
xfs_da_btree.h xfs: remove the dead XFS_DABUF_DEBUG code 2011-07-13 13:43:50 +02:00
xfs_dfrag.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_dfrag.h
xfs_dinode.h xfs: Remove the macro XFS_BUF_PTR 2011-07-25 15:03:13 -05:00
xfs_dir2_block.c xfs: reshuffle dir2 headers 2011-07-13 13:43:48 +02:00
xfs_dir2_data.c xfs: reshuffle dir2 headers 2011-07-13 13:43:48 +02:00
xfs_dir2_format.h xfs: cleanup struct xfs_dir2_free 2011-07-13 13:43:48 +02:00
xfs_dir2_leaf.c xfs: introduce xfs_bmapi_read() 2011-10-11 21:15:03 -05:00
xfs_dir2_node.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-07-25 13:56:39 -07:00
xfs_dir2_priv.h xfs: reshuffle dir2 headers 2011-07-13 13:43:48 +02:00
xfs_dir2_sf.c xfs: reshuffle dir2 headers 2011-07-13 13:43:48 +02:00
xfs_dir2.c xfs: get rid of open-coded S_ISREG(), etc. 2011-07-26 15:05:16 -04:00
xfs_dir2.h xfs: reshuffle dir2 headers 2011-07-13 13:43:48 +02:00
xfs_discard.c xfs: fix possible overflow in xfs_ioc_trim() 2011-10-11 21:15:07 -05:00
xfs_discard.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_dquot_item.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_dquot_item.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_dquot.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_dquot.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_error.c xfs: Convert remaining cmn_err() callers to new API 2011-03-07 10:08:35 +11:00
xfs_error.h xfs: kill support/debug.[ch] 2011-03-07 10:09:35 +11:00
xfs_export.c xfs: unlock the inode before log force in xfs_fs_nfs_commit_metadata 2011-10-11 21:15:08 -05:00
xfs_export.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_extfree_item.c xfs: fix efi item leak on forced shutdown 2011-01-28 09:01:33 -06:00
xfs_extfree_item.h xfs: Pull EFI/EFD handling out from under the AIL lock 2010-12-20 11:59:49 +11:00
xfs_file.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_filestream.c xfs: rename allocation range fields in struct xfs_bmalloca 2011-10-11 21:15:06 -05:00
xfs_filestream.h xfs: clean up filestreams helpers 2010-07-26 13:16:51 -05:00
xfs_fs_subr.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_fs.h xfs: consolidate & clarify mount sanity checks 2011-07-08 11:32:51 -05:00
xfs_fsops.c xfs: Check the return value of xfs_buf_get() 2011-10-11 21:15:01 -05:00
xfs_fsops.h xfs: ensure log covering transactions are synchronous 2011-01-11 20:28:17 -06:00
xfs_globals.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_ialloc_btree.c xfs: remove leftovers of the old btree tracing code 2011-07-13 13:43:50 +02:00
xfs_ialloc_btree.h
xfs_ialloc.c xfs: Check the return value of xfs_trans_get_buf() 2011-10-11 21:15:01 -05:00
xfs_ialloc.h
xfs_iget.c xfs: remove i_iocount 2011-10-11 21:15:01 -05:00
xfs_inode_item.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_inode_item.h xfs: simplify inode to transaction joining 2010-07-26 13:16:36 -05:00
xfs_inode.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_inode.h xfs: remove i_iocount 2011-10-11 21:15:01 -05:00
xfs_inum.h xfs: cleanup shortform directory inode number handling 2011-07-08 14:35:03 +02:00
xfs_ioctl32.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_ioctl32.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_ioctl.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_ioctl.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_iomap.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_iomap.h xfs: kill xfs_iomap 2010-12-16 16:05:51 -06:00
xfs_iops.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_iops.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_itable.c xfs: fix variable set but not used warnings 2011-04-08 08:09:12 -05:00
xfs_itable.h xfs: remove block number from inode lookup code 2010-06-24 11:35:17 +10:00
xfs_linux.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_log_cil.c xfs: add online discard support 2011-05-24 11:17:13 -05:00
xfs_log_priv.h xfs: exact busy extent tracking 2011-04-28 13:18:04 -05:00
xfs_log_recover.c xfs: let xfs_bwrite callers handle the xfs_buf_relse 2011-10-11 21:15:00 -05:00
xfs_log_recover.h xfs: Clean up XFS_BLI_* flag namespace 2010-05-24 10:33:39 -05:00
xfs_log.c xfs: Remove the macro XFS_BUF_SET_PTR 2011-07-25 15:03:17 -05:00
xfs_log.h xfs: exact busy extent tracking 2011-04-28 13:18:04 -05:00
xfs_message.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_message.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_mount.c xfs: call xfs_buf_delwri_queue directly 2011-10-11 21:14:59 -05:00
xfs_mount.h xfs: Remove the second parameter to xfs_sb_count() 2011-07-20 18:35:03 -05:00
xfs_mru_cache.c xfs: convert to alloc_workqueue() 2011-02-01 11:42:43 +01:00
xfs_mru_cache.h
xfs_qm_bhv.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_qm_stats.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_qm_stats.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_qm_syscalls.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_qm.c xfs: introduce xfs_bmapi_read() 2011-10-11 21:15:03 -05:00
xfs_qm.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_quota_priv.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_quota.h xfs: Convert xlog_warn to new logging interface 2011-03-07 10:01:35 +11:00
xfs_quotaops.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_rename.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_rtalloc.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_rtalloc.h xfs: Remove the macro XFS_BUF_PTR 2011-07-25 15:03:13 -05:00
xfs_rw.c xfs: call xfs_buf_delwri_queue directly 2011-10-11 21:14:59 -05:00
xfs_rw.h
xfs_sb.h xfs: Remove the macro XFS_BUF_PTR 2011-07-25 15:03:13 -05:00
xfs_stats.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_stats.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_super.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_super.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_sync.c xfs: remove i_iocount 2011-10-11 21:15:01 -05:00
xfs_sync.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_sysctl.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_sysctl.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_trace.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_trace.h xfs: call xfs_buf_delwri_queue directly 2011-10-11 21:14:59 -05:00
xfs_trans_ail.c xfs: set cursor in xfs_ail_splice() even when AIL was empty 2011-08-09 15:30:43 -05:00
xfs_trans_buf.c xfs: call xfs_buf_delwri_queue directly 2011-10-11 21:14:59 -05:00
xfs_trans_dquot.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_trans_extfree.c xfs: Pull EFI/EFD handling out from under the AIL lock 2010-12-20 11:59:49 +11:00
xfs_trans_inode.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_trans_priv.h xfs: convert AIL cursors to use struct list_head 2011-07-20 18:37:46 -05:00
xfs_trans_space.h
xfs_trans.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_trans.h xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_types.h xfs: exact busy extent tracking 2011-04-28 13:18:04 -05:00
xfs_utils.c xfs: remove xfs_cred.h 2010-10-18 15:08:06 -05:00
xfs_utils.h xfs: remove xfs_cred.h 2010-10-18 15:08:06 -05:00
xfs_vnode.h xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs_vnodeops.c xfs: simplify xfs_trans_ijoin* again 2011-10-11 21:15:08 -05:00
xfs_vnodeops.h xfs: split xfs_setattr 2011-07-08 14:34:23 +02:00
xfs_xattr.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
xfs.h xfs: don't expect xfs headers to be in subdirectories 2011-08-12 13:57:55 -05:00