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authorMatthew Ahrens <[email protected]>2016-05-12 21:16:36 -0700
committerBrian Behlendorf <[email protected]>2017-06-09 09:43:26 -0700
commitdbeb8796996b4a342f7de2b3eb4ea5b86ac260f9 (patch)
tree63a722cfe2ae86634005064399b5672e3694eeb8 /include/sys/dmu_objset.h
parent1b7c1e5ce90ae27d9bb1f6f3616bf079c168005c (diff)
OpenZFS 8199 - multi-threaded dmu_object_alloc()
dmu_object_alloc() is single-threaded, so when multiple threads are creating files in a single filesystem, they spend a lot of time waiting for the os_obj_lock. To improve performance of multi-threaded file creation, we must make dmu_object_alloc() typically not grab any filesystem-wide locks. The solution is to have a "next object to allocate" for each CPU. Each of these "next object"s is in a different block of the dnode object, so that concurrent allocation holds dnodes in different dbufs. When a thread's "next object" reaches the end of a chunk of objects (by default 4 blocks worth -- 128 dnodes), it will be reset to the per-objset os_obj_next, which will be increased by a chunk of objects (128). Only when manipulating the os_obj_next will we need to grab the os_obj_lock. This decreases lock contention dramatically, because each thread only needs to grab the os_obj_lock briefly, once per 128 allocations. This results in a 70% performance improvement to multi-threaded object creation (where each thread is creating objects in its own directory), from 67,000/sec to 115,000/sec, with 8 CPUs. Work sponsored by Intel Corp. Authored by: Matthew Ahrens <[email protected]> Reviewed-by: Ned Bass <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Ported-by: Matthew Ahrens <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> OpenZFS-issue: https://www.illumos.org/issues/8199 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/374 Closes #4703 Closes #6117
Diffstat (limited to 'include/sys/dmu_objset.h')
-rw-r--r--include/sys/dmu_objset.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/sys/dmu_objset.h b/include/sys/dmu_objset.h
index 636b0e249..a836e0372 100644
--- a/include/sys/dmu_objset.h
+++ b/include/sys/dmu_objset.h
@@ -120,7 +120,11 @@ struct objset {
/* Protected by os_obj_lock */
kmutex_t os_obj_lock;
- uint64_t os_obj_next;
+ uint64_t os_obj_next_chunk;
+
+ /* Per-CPU next object to allocate, protected by atomic ops. */
+ uint64_t *os_obj_next_percpu;
+ int os_obj_next_percpu_len;
/* Protected by os_lock */
kmutex_t os_lock;