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Subjectfs: Inode cache scalability V2
Date
This patch set is derived from Nick Piggin's VFS scalability tree.
there doesn't appear to be any push to get that tree into shape for
.37, so this is an attempt to get finer grained review of the series
for upstream inclusion. I'm hitting VFS lock contention problems
with XFS on 8-16p machines now, so I need to get this stuff moving.

This patch set is just the basic inode_lock breakup patches plus a
few more simple changes to the inode code. It stops short of
introducing RCU inode freeing because those changes are not
completely baked yet.

As a result, the full inode handling improvements of Nick's patch
set are not realised with this short series. However, my own testing
indicates that the amount of lock traffic and contention is down by
an order of magnitude on an 8-way box for parallel inode create and
unlink workloads, so there is still significant improvements from
just this patch set.

Version 2 of this series is a complete rework of the original patch
series. Nick's original code nested list locks inside the the
inode->i_lock, resulting in a large mess of trylock operations to
get locks out of order all over the place. In many cases, the reason
fo this lock ordering is removed later on in Nick's series as
cleanups are introduced.

As a result I've pulled in several of the cleanups and re-ordered
the series such that cleanups, factoring and list splitting are done
before any of the locking changes. Instead of converting the inode
state flags first, I've converted them last, ensuring that
manipulations are kept inside other locks rather than outside them.

The series is made up of the following steps:

- inode counters are made per-cpu
- inode LRU manipulations are made lazy
- i_list is split into two lists (grows inode by 2
pointers), one for tracking lru status, one for writeback
status
- reference counting is factored, then renamed and locked
differently
- inode hash operations are factored, then locked per bucket
- superblock inode listis locked per-superblock
- inode LRU is locked via a global lock
- unclear what the best way to split this up from
here is, so no attempt is made to optimise
further.
- Currently not showing signs of contention under
any workload on an 8p machine.
- inode IO list are locked via a per-BDI lock
- further analysis needed to determine the next step
in optimising this list. It is extremely contended
under parallel workloads because foreground
throttling (balance_dirty_pages) causes unbound
writeback parallelism and contention. Fixing the
unbound parallelism, I think, is a more important
first optimisation step than making the list
per-cpu.
- lock i_state operations with i_lock
- convert last_ino allocation to a percpu counter
- protect iunique counter with it's own lock
- remove inode_lock
- kill dispose_list() and factor destroying an inode into
dispose_one_inode() which is called from reclaim, unmount
and iput_final.

None of the patcheѕ are unchanged, and several of them are new or
completely rewritten, so any previous testing is completely
invalidated. I have not tried to optimise locking by using trylock
loops - anywhere that requires out-of-order locking drops locks and
regains the locks needed for the next operation. This approach
simplified the code and lead to several improvments in the patch
series (e.g. moving inode->i_lock inside writeback_single_inode(),
and the dispose_one_inode factoring) that would have gone unnoticed
if I'd gone down the same trylock loop path that Nick used.

I've done some testing so far on ext3, ext4 and XFS (mostly sanity
and lock_stat profile testing), but I have not tested any other
filesystems. IOWs, it is light on testing at this point. I'm sending
out for review now that it passes basic sanity tests so that
comments on the reworked approach can be made.

Version 2:
- complete rework of series.

--

The following changes since commit cb655d0f3d57c23db51b981648e452988c0223f9:

Linux 2.6.36-rc7 (2010-10-06 13:39:52 -0700)

are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/dgc/xfsdev.git inode-scale

Dave Chinner (11):
fs: Convert nr_inodes and nr_unused to per-cpu counters
fs: Clean up inode reference counting
exofs: use iput() for inode reference count decrements
fs: add inode reference coutn read accessor
fs: rework icount to be a locked variable
fs: Factor inode hash operations into functions
fs: add a per-superblock lock for the inode list
fs: split locking of inode writeback and LRU lists
fs: Protect inode->i_state with th einode->i_lock
fs: icache remove inode_lock
fs: Reduce inode I_FREEING and factor inode disposal

Eric Dumazet (1):
fs: introduce a per-cpu last_ino allocator

Nick Piggin (6):
kernel: add bl_list
fs: keep inode with backing-dev
fs: Implement lazy LRU updates for inodes.
fs: inode split IO and LRU lists
fs: Introduce per-bucket inode hash locks
fs: Make iunique independent of inode_lock

Documentation/filesystems/Locking | 2 +-
Documentation/filesystems/porting | 10 +-
Documentation/filesystems/vfs.txt | 2 +-
arch/powerpc/platforms/cell/spufs/file.c | 2 +-
drivers/char/mem.c | 2 +-
drivers/char/raw.c | 2 +-
drivers/mtd/mtdchar.c | 2 +-
drivers/staging/pohmelfs/inode.c | 10 +-
fs/9p/vfs_inode.c | 5 +-
fs/affs/inode.c | 2 +-
fs/afs/dir.c | 2 +-
fs/afs/write.c | 6 +-
fs/anon_inodes.c | 5 +-
fs/bfs/dir.c | 2 +-
fs/block_dev.c | 26 +-
fs/btrfs/disk-io.c | 2 +-
fs/btrfs/file.c | 2 +-
fs/btrfs/inode.c | 28 +-
fs/buffer.c | 4 +-
fs/ceph/addr.c | 2 +-
fs/ceph/inode.c | 4 +-
fs/ceph/mds_client.c | 2 +-
fs/cifs/file.c | 2 +-
fs/cifs/inode.c | 4 +-
fs/coda/dir.c | 2 +-
fs/configfs/inode.c | 3 +-
fs/drop_caches.c | 19 +-
fs/exofs/inode.c | 6 +-
fs/exofs/namei.c | 2 +-
fs/ext2/ialloc.c | 2 +-
fs/ext2/namei.c | 2 +-
fs/ext3/ialloc.c | 4 +-
fs/ext3/namei.c | 2 +-
fs/ext4/ialloc.c | 4 +-
fs/ext4/namei.c | 2 +-
fs/fs-writeback.c | 184 ++++----
fs/fuse/file.c | 6 +-
fs/fuse/inode.c | 2 +-
fs/gfs2/glock.c | 3 +-
fs/gfs2/ops_inode.c | 2 +-
fs/hfs/hfs_fs.h | 2 +-
fs/hfs/inode.c | 2 +-
fs/hfsplus/dir.c | 2 +-
fs/hfsplus/hfsplus_fs.h | 2 +-
fs/hfsplus/inode.c | 2 +-
fs/hpfs/inode.c | 2 +-
fs/hugetlbfs/inode.c | 3 +-
fs/inode.c | 764 ++++++++++++++++++++----------
fs/internal.h | 6 +
fs/jffs2/dir.c | 4 +-
fs/jfs/jfs_txnmgr.c | 2 +-
fs/jfs/namei.c | 2 +-
fs/libfs.c | 2 +-
fs/locks.c | 2 +-
fs/logfs/dir.c | 2 +-
fs/logfs/inode.c | 2 +-
fs/logfs/readwrite.c | 2 +-
fs/minix/namei.c | 2 +-
fs/namei.c | 2 +-
fs/nfs/dir.c | 2 +-
fs/nfs/getroot.c | 2 +-
fs/nfs/inode.c | 7 +-
fs/nfs/nfs4state.c | 2 +-
fs/nfs/write.c | 9 +-
fs/nilfs2/btnode.c | 2 +-
fs/nilfs2/gcdat.c | 1 +
fs/nilfs2/gcinode.c | 22 +-
fs/nilfs2/mdt.c | 7 +-
fs/nilfs2/namei.c | 2 +-
fs/nilfs2/segment.c | 2 +-
fs/nilfs2/the_nilfs.c | 2 +-
fs/nilfs2/the_nilfs.h | 2 +-
fs/notify/inode_mark.c | 47 ++-
fs/notify/mark.c | 1 -
fs/notify/vfsmount_mark.c | 1 -
fs/ntfs/file.c | 2 +-
fs/ntfs/inode.c | 4 +-
fs/ntfs/super.c | 4 +-
fs/ocfs2/dlmfs/dlmfs.c | 4 +-
fs/ocfs2/file.c | 2 +-
fs/ocfs2/inode.c | 2 +-
fs/ocfs2/namei.c | 2 +-
fs/quota/dquot.c | 32 +-
fs/ramfs/inode.c | 2 +-
fs/reiserfs/namei.c | 2 +-
fs/reiserfs/stree.c | 2 +-
fs/reiserfs/xattr.c | 2 +-
fs/romfs/super.c | 4 +-
fs/smbfs/inode.c | 2 +-
fs/super.c | 1 +
fs/sysfs/inode.c | 2 +-
fs/sysv/namei.c | 2 +-
fs/ubifs/dir.c | 4 +-
fs/ubifs/super.c | 4 +-
fs/udf/namei.c | 2 +-
fs/ufs/namei.c | 2 +-
fs/xfs/linux-2.6/xfs_buf.c | 4 +-
fs/xfs/linux-2.6/xfs_file.c | 2 +-
fs/xfs/linux-2.6/xfs_iops.c | 2 +-
fs/xfs/linux-2.6/xfs_trace.h | 2 +-
fs/xfs/xfs_inode.h | 4 +-
include/linux/backing-dev.h | 17 +-
include/linux/fs.h | 34 +-
include/linux/list_bl.h | 127 +++++
include/linux/poison.h | 2 +
include/linux/writeback.h | 13 +-
ipc/mqueue.c | 2 +-
kernel/cgroup.c | 2 +-
kernel/futex.c | 2 +-
kernel/sysctl.c | 4 +-
mm/backing-dev.c | 90 ++++-
mm/fadvise.c | 4 +-
mm/filemap.c | 10 +-
mm/filemap_xip.c | 2 +-
mm/page-writeback.c | 15 +-
mm/readahead.c | 6 +-
mm/rmap.c | 6 +-
mm/shmem.c | 8 +-
mm/swap.c | 2 +-
mm/swap_state.c | 2 +-
mm/swapfile.c | 2 +-
mm/truncate.c | 3 +-
mm/vmscan.c | 2 +-
net/socket.c | 2 +-
124 files changed, 1131 insertions(+), 616 deletions(-)
create mode 100644 include/linux/list_bl.h
--
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