[PATCH for-next v1 0/2] enable pcpu bio-cache for IRQ uring-passthru I/O

[Kanchan Joshi]

On Tue, Jan 17, 2023 at 10:11:08AM -0700, Jens Axboe wrote:
>On 1/17/23 5:06?AM, Anuj Gupta wrote:
>> This series extends bio pcpu caching for normal / IRQ-driven
>> uring-passthru I/Os. Earlier, only polled uring-passthru I/Os could
>> leverage bio-cache. After the series from Pavel[1], bio-cache can be
>> leveraged by normal / IRQ driven I/Os as well. t/io_uring with an Optane
>> SSD setup shows +7.21% for batches of 32 requests.
>>
>> [1] https://lore.kernel.org/io-uring/cover.1666347703.git.asml.silence@gmail.com/
>>
>> IRQ, 128/32/32, cache off
>
>Tests here -
>
>before:
>
>polled=0, fixedbufs=1/0, register_files=1, buffered=1, QD=128
>Engine=io_uring, sq_ring=128, cq_ring=128
>IOPS=62.88M, BW=30.70GiB/s, IOS/call=32/31
>IOPS=62.95M, BW=30.74GiB/s, IOS/call=32/31
>IOPS=62.52M, BW=30.53GiB/s, IOS/call=32/32
>IOPS=62.61M, BW=30.57GiB/s, IOS/call=31/32
>IOPS=62.52M, BW=30.53GiB/s, IOS/call=32/31
>IOPS=62.40M, BW=30.47GiB/s, IOS/call=32/32
>
>after:
>
>polled=0, fixedbufs=1/0, register_files=1, buffered=1, QD=128
>Engine=io_uring, sq_ring=128, cq_ring=128
>IOPS=76.58M, BW=37.39GiB/s, IOS/call=31/31
>IOPS=79.42M, BW=38.78GiB/s, IOS/call=32/32
>IOPS=78.06M, BW=38.12GiB/s, IOS/call=31/31
>IOPS=77.64M, BW=37.91GiB/s, IOS/call=32/31
>IOPS=77.17M, BW=37.68GiB/s, IOS/call=32/32
>IOPS=76.73M, BW=37.47GiB/s, IOS/call=31/31
>IOPS=76.94M, BW=37.57GiB/s, IOS/call=32/31
>
>Note that this includes Pavel's fix as well:
>
>https://lore.kernel.org/linux-block/80d4511011d7d4751b4cf6375c4e38f237d935e3.1673955390.git.asml.silence@gmail.com/

So I was thinking whether we need this fix for passthru path too. We do
not.
For block path, blk_mq_get_cached_request() encountered a
mismatch since type was different (read vs default).
For passthru, blk_mq_alloc_cached_request() sees no mismatch since
passthrough opf is not treated as read (default vs default).