Re: [PATCH 0/2] blk-mq: stop waiting for an SRCU grace period when freeing a tag set

[Qiliang Yuan]

Hi Jens, Ming,

Gentle ping on this series. Paul acked it from the RCU side, and it
still needs a look from the block side.

Since I sent it, "ublk: drop the device reference outside
ublk_ctl_mutex in DEL_DEV" has been applied to for-7.4/block, so ublk
no longer frees tag sets under a global lock and the 19 s figure in
the cover letter is out of date. The SRCU grace period that every
blk_mq_free_tag_set() waits for is still there. With 4000 single-queue
ublk devices on 7.3-rc5 plus that commit, median of 3 runs:

                                 without      with this series
  DEL_DEV p50, serial             3.41ms           0.17ms
  deletion with 16 threads         4.17s            2.87s

Thanks,
Qiliang