Commits on May 31, 2022

1. zvol: Support blk-mq for better performance …

   Add support for the kernel's block multiqueue (blk-mq) interface in
   the zvol block driver.  blk-mq creates multiple request queues on
   different CPUs rather than having a single request queue.  This can
   improve zvol performance with multithreaded reads/writes.
   
   This implementation uses the blk-mq interfaces on 4.13 or newer
   kernels.  Building against older kernels will fall back to the
   older BIO interfaces.
   
   Note that you must set the `zvol_use_blk_mq` module param to
   enable the blk-mq API.  It is disabled by default.
   
   In addition, this commit lets the zvol blk-mq layer process whole
   `struct request` IOs at a time, rather than breaking them down
   into their individual BIOs.  This reduces dbuf lock contention
   and overhead versus the legacy zvol submit_bio() codepath.
   
   	sequential dd to one zvol, 8k volblocksize, no O_DIRECT:
   
   	legacy submit_bio()     292MB/s write  453MB/s read
   	this commit             453MB/s write  885MB/s read
   
   It also introduces a new `zvol_blk_mq_chunks_per_thread` module
   parameter. This parameter represents how many volblocksize'd chunks
   to process per each zvol thread.  It can be used to tune your zvols
   for better read vs write performance (higher values favor write,
   lower favor read).
   
   Signed-off-by: Tony Hutter <hutter2@llnl.gov>
   Issue openzfs#12483

   

   tonyhutter committed May 31, 2022
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