Andriy Gapon 5386d7295a MFV r316917: 7968 multi-threaded spa_sync() ... illumos/illumos-gate@94c2d0eb22 94c2d0eb22 https://www.illumos.org/issues/7968 spa_sync() iterates over all the dirty dnodes and processes each of them by calling dnode_sync(). If there are many dirty dnodes (e.g. because we created or removed a lot of files), the single thread of spa_sync() calling dnode_sync() can become a bottleneck. Additionally, if many dnodes are dirtied concurrently in open context (e.g. due to concurrent file creation), the os_lock will experience lock contention via dnode_setdirty(). The solution is to track dirty dnodes on a multilist_t, and for spa_sync() to use separate threads to process each of the sublists in the multilist. On the concurrent file creation microbenchmark, the performance improvement from dnode_setdirty() is up to 7%. Additionally, the wall clock time spent in spa_sync() is reduced to 15%-40% of the single-threaded case. In terms of cost/ reward, once the other bottlenecks are addressed, fixing this bug will provide a medium-large performance gain and require a medium amount of effort to implement. Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@omniti.com> Author: Matthew Ahrens <mahrens@delphix.com> MFC after: 3 weeks		2017-05-24 22:21:24 +00:00
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common	MFV 316891	2017-04-21 19:53:52 +00:00
uts	MFV r316917: 7968 multi-threaded spa_sync()	2017-05-24 22:21:24 +00:00
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