Linux 6.4 Lands Concurrent I/O Performance Optimizations For Device Mapper

Written by Michael Larabel in Linux Storage on 2 May 2023 at 06:21 AM EDT. 1 Comment
LINUX STORAGE
The Device Mapper "DM" subsystem updates have been merged for the in-development Linux 6.4 kernel and it includes some notable performance optimizations.

As I wrote about back in March, Device Mapper was set to see improved concurrent I/O performance. That DM performance work has successfully landed for Linux 6.4. That concurrent I/O work is significant in that in some cases for acquiring buffers can be as much as twenty-five times faster.

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Per the DM merge to Linux Git some of the highlights for the Device Mapper code this cycle includes:
- Split dm-bufio's rw_semaphore and rbtree. Offers improvements to dm-bufio's locking to allow increased concurrent IO -- particularly for read access for buffers already in dm-bufio's cache.

- Also split dm-bio-prison-v1's spinlock and rbtree with comparable aim at improving concurrent IO (for the DM thinp target).

- Both the dm-bufio and dm-bio-prison-v1 scaling of the number of locks and rbtrees used are managed by dm_num_hash_locks(). And the hash function used by both is dm_hash_locks_index().

- Allow DM targets to require DISCARD, WRITE_ZEROES and SECURE_ERASE to be split at the target specified boundary (in terms of max_discard_sectors, max_write_zeroes_sectors and max_secure_erase_sectors respectively).

- DM core ->io_hints improvements needed in support of new discard support that is added to the DM "zero" and "error" targets.

- Various small improvements to both DM core and DM targets.
Linux 6.4 has been a very active merge window thus far, which ends this weekend, with many new features and optimizations having been introduced.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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