Merge tag 'xfs-cil-scale-2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs into xfs-5.14-merge2-cilxfs-5.14-merge-2

xfs: CIL and log scalability improvements

Performance improvements are largely documented in the change logs of the
individual patches. Headline numbers are an increase in transaction rate from
700k commits/s to 1.7M commits/s, and a reduction in fua/flush operations by
2-3 orders of magnitude on metadata heavy workloads that don't use fsync.

Summary of series:

Patches         Modifications
-------         -------------
1-7:            log write FUA/FLUSH optimisations
8:              bug fix
9-11:           Async CIL pushes
12-25:          xlog_write() rework
26-39:          CIL commit scalability

The log write FUA/FLUSH optimisations reduce the number of cache flushes
required to flush the CIL to the journal. It extends the old pre-delayed logging
ordering semantics required by writing individual transactions to the iclogs out
to cover then CIL checkpoint transactions rather than individual writes to the
iclogs. In doing so, we reduce the cache flush requirements to once per CIL
checkpoint rather than once per iclog write.

The async CIL pushes fix a pipeline limitation that only allowed a single CIL
push to be processed at a time. This was causing CIL checkpoint writing to
become CPU bound as only a single CIL checkpoint could be pushed at a time. The
checkpoint pipleine was designed to allow multiple pushes to be in flight at
once and use careful ordering of the commit records to ensure correct recovery
order, but the workqueue implementation didn't allow concurrent works to be run.
The concurrent works now extend out to 4 CIL checkpoints running at a time,
hence removing the CPU usage limiations without introducing new lock contention
issues.

The xlog_write() rework is long overdue. The code is complex, difficult to
understand, full of tricky, subtle corner cases and just generally really hard
to modify. This patchset reworks the xlog_write() API to reduce the processing
overhead of writing out long log vector chains, and factors the xlog_write()
code into a simple, compact fast path along with a clearer slow path to handle
the complex cases.

The CIL commit scalability patchset removes spinlocks from the transaction
commit fast path. These spinlocks are the performance limiting bottleneck in the
transaction commit path, so we apply a variety of different techniques to do
either atomic. lockless or per-cpu updates of the CIL tracking structures during
commits. This greatly increases the throughput of the the transaction commit
engine, moving the contention point to the log space tracking algorithms after
doubling throughput on 32-way workloads.

* tag 'xfs-cil-scale-2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs: (40 commits)
  xfs: expanding delayed logging design with background material
  xfs: xlog_sync() manually adjusts grant head space
  xfs: avoid cil push lock if possible
  xfs: move CIL ordering to the logvec chain
  xfs: convert log vector chain to use list heads
  xfs: convert CIL to unordered per cpu lists
  xfs: Add order IDs to log items in CIL
  xfs: convert CIL busy extents to per-cpu
  xfs: track CIL ticket reservation in percpu structure
  xfs: implement percpu cil space used calculation
  xfs: introduce per-cpu CIL tracking structure
  xfs: introduce CPU hotplug infrastructure
  xfs: rework per-iclog header CIL reservation
  xfs: lift init CIL reservation out of xc_cil_lock
  xfs: use the CIL space used counter for emptiness checks
  xfs: CIL context doesn't need to count iovecs
  xfs: xlog_write() doesn't need optype anymore
  xfs: xlog_write() no longer needs contwr state
  xfs:_introduce xlog_write_partial()
  xfs: introduce xlog_write_single()
  ...

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 4a62b3980642..bf8f29ad9bf8 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -52,6 +52,7 @@ enum cpuhp_state {
 	CPUHP_FS_BUFF_DEAD,
 	CPUHP_PRINTK_DEAD,
 	CPUHP_MM_MEMCQ_DEAD,
+	CPUHP_XFS_DEAD,
 	CPUHP_PERCPU_CNT_DEAD,
 	CPUHP_RADIX_DEAD,
 	CPUHP_PAGE_ALLOC_DEAD,