diff options
| author | Yu Kuai <yukuai@fnnas.com> | 2026-02-03 11:19:49 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2026-02-03 17:45:37 +0300 |
| commit | 2c04718edcd5e1ac8fed9a0f8d0620e8bc94014d (patch) | |
| tree | 359c598fe2615fbbf77d17774347e3c244d3fc73 | |
| parent | 2110858c5178176d0d535b7762b20cb9c0d03146 (diff) | |
| download | linux-2c04718edcd5e1ac8fed9a0f8d0620e8bc94014d.tar.xz | |
blk-mq: add documentation for new queue attribute async_dpeth
Explain the attribute and the default value in different case.
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | Documentation/ABI/stable/sysfs-block | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block index 0ed10aeff86b..aa1e94169666 100644 --- a/Documentation/ABI/stable/sysfs-block +++ b/Documentation/ABI/stable/sysfs-block @@ -609,6 +609,40 @@ Description: enabled, and whether tags are shared. +What: /sys/block/<disk>/queue/async_depth +Date: August 2025 +Contact: linux-block@vger.kernel.org +Description: + [RW] Controls how many asynchronous requests may be allocated in the + block layer. The value is always capped at nr_requests. + + When no elevator is active (none): + - async_depth is always equal to nr_requests. + + For bfq scheduler: + - By default, async_depth is set to 75% of nr_requests. + Internal limits are then derived from this value: + * Sync writes: limited to async_depth (≈75% of nr_requests). + * Async I/O: limited to ~2/3 of async_depth (≈50% of nr_requests). + + If a bfq_queue is weight-raised: + * Sync writes: limited to ~1/2 of async_depth (≈37% of nr_requests). + * Async I/O: limited to ~1/4 of async_depth (≈18% of nr_requests). + + - If the user writes a custom value to async_depth, BFQ will recompute + these limits proportionally based on the new value. + + For Kyber: + - By default async_depth is set to 75% of nr_requests. + - If the user writes a custom value to async_depth, then it override the + default and directly control the limit for writes and async I/O. + + For mq-deadline: + - By default async_depth is set to nr_requests. + - If the user writes a custom value to async_depth, then it override the + default and directly control the limit for writes and async I/O. + + What: /sys/block/<disk>/queue/nr_zones Date: November 2018 Contact: Damien Le Moal <damien.lemoal@wdc.com> |