linux-kernel - Re: [PATCH 00/17] ublk: avoid accessing ublk_queue to handle ublksrv_io

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Message-Id: <175837194548.917590.3460504068129272434.b4-ty@kernel.dk>
Date: Sat, 20 Sep 2025 06:39:05 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Ming Lei <ming.lei@...hat.com>, 
 Caleb Sander Mateos <csander@...estorage.com>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/17] ublk: avoid accessing ublk_queue to handle
 ublksrv_io_cmd


On Wed, 17 Sep 2025 19:49:36 -0600, Caleb Sander Mateos wrote:
> For ublk servers with many ublk queues, accessing the ublk_queue in
> ublk_ch_uring_cmd_local() and the functions it calls is a frequent cache miss.
> The ublk_queue is only accessed for its q_depth and flags, which are also
> available on ublk_device. And ublk_device is already accessed for nr_hw_queues,
> so it will already be cached. Unfortunately, the UBLK_IO_NEED_GET_DATA path
> still needs to access the ublk_queue for io_cmd_buf, so it's not possible to
> avoid accessing the ublk_queue there. (Allocating a single io_cmd_buf for all of
> a ublk_device's I/Os could be done in the future.) At least we can optimize
> UBLK_IO_FETCH_REQ, UBLK_IO_COMMIT_AND_FETCH_REQ, UBLK_IO_REGISTER_IO_BUF, and
> UBLK_IO_UNREGISTER_IO_BUF.
> Using only the ublk_device and not the ublk_queue in ublk_dispatch_req() is also
> possible, but left for a future change.
> 
> [...]

Applied, thanks!

[01/17] ublk: remove ubq check in ublk_check_and_get_req()
        commit: 163f80dabf4f0c4d9e6c39e0dba474814dac78f8
[02/17] ublk: don't pass q_id to ublk_queue_cmd_buf_size()
        commit: b7e255b0340b5319fca4fe076119d0f929a24305
[03/17] ublk: don't pass ublk_queue to __ublk_fail_req()
        commit: 0265595002b989db8e0c32dc33624fa61a974b20
[04/17] ublk: add helpers to check ublk_device flags
        commit: d74a383ec70de33ae6577af889556747d6693269
[05/17] ublk: don't dereference ublk_queue in ublk_ch_uring_cmd_local()
        commit: 5125535f90564117506d926d0de92c4c2622b720
[06/17] ublk: don't dereference ublk_queue in ublk_check_and_get_req()
        commit: b40dcdf8235d536072b9f61eb6d291f0f3720768
[07/17] ublk: pass ublk_device to ublk_register_io_buf()
        commit: 8a81926e45670c6d9b6e73e0482485d5c9a627e6
[08/17] ublk: don't access ublk_queue in ublk_register_io_buf()
        commit: 692cf47e1af39f86f28069db5ca6b00a7d2daddc
[09/17] ublk: don't access ublk_queue in ublk_daemon_register_io_buf()
        commit: ce88e3ef33d35c740d26342be5d8f65972fd5597
[10/17] ublk: pass q_id and tag to __ublk_check_and_get_req()
        commit: 25c028aa791503fe0876c20bfd67b2676e6e24d0
[11/17] ublk: don't access ublk_queue in ublk_check_fetch_buf()
        commit: a689efd5fde7b39cfbcf43267bccf0e56295cc16
[12/17] ublk: don't access ublk_queue in ublk_config_io_buf()
        commit: 23c014448e97d4b59c54816f545ab963bf8dd644
[13/17] ublk: don't pass ublk_queue to ublk_fetch()
        commit: 3576e60a33c7f6be024b80f8c87312032fd27892
[14/17] ublk: don't access ublk_queue in ublk_check_commit_and_fetch()
        commit: be7962d7e3d9dd9ff5b6bcd3faccb3b0f76a9734
[15/17] ublk: don't access ublk_queue in ublk_need_complete_req()
        commit: 122f6387e845dfbfcf1ed795734a1ec779e987f0
[16/17] ublk: pass ublk_io to __ublk_complete_rq()
        commit: 97a02be6303646e19e9092042928b0e13543305c
[17/17] ublk: don't access ublk_queue in ublk_unmap_io()
        commit: 755a18469ca4eca3b5bb4f52704b7708a9106db9

Best regards,
-- 
Jens Axboe