505df8d133
Incorrectly sizing the array of hash locks used to protect the dbuf hash table can lead to contention and reduce performance. We could unconditionally allocate a larger array for the locks but it's wasteful, particularly for a low-memory system. Instead, dynamically allocate the array of locks and scale it based on total system memory. Additionally, add a new `dbuf_mutex_cache_shift` module option which can be used to override the hash lock array size. This is disabled by default (dbuf_mutex_hash_shift=0) and can only be set at module load time. The minimum target array size is set to 8192, this matches the current constant value. Note that the count of the dbuf hash table and count of the mutex array were added to the /proc/spl/kstat/zfs/dbufstats kstat. Finally, this change removes the _KERNEL conditional checks. These were not required since for the user space build there is no difference between the kmem and vmem interfaces. Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Alexander Motin <mav@FreeBSD.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #13928 |
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