Re: [RFC PATCH 0/4] Read/Write with meta buffer

[Jens Axboe <axboe@kernel.dk>]

On 3/22/24 12:50 PM, Kanchan Joshi wrote:
> This patchset is aimed at getting the feedback on a new io_uring
> interface that userspace can use to exchange meta buffer along with
> read/write.
> 
> Two new opcodes for that: IORING_OP_READ_META and IORING_OP_WRITE_META.
> The leftover space in the SQE is used to send meta buffer pointer
> and its length. Patch #2 for this.
> 
> The interface is supported for block direct IO. Patch #4 for this.
> Other two are prep patches.
> 
> It has been tried not to touch the hot read/write path, as much as
> possible. Performance for non-meta IO is same after the patches [2].
> There is some code in the cold path (worker-based async)
> though.

This patchset should look cleaner if you rebase it on top of the current
for-6.10/io_uring branch, as it gets rid of the async nastiness. Since
that'll need doing anyway, could you repost a v2 where it's rebased on
top of that?

Also in terms of the cover letter, would be good with a bit more of a
description of what this enables. It's a bit scant on detail on what
exactly this gives you.

> taskset -c 2,5 t/io_uring -b512 -d128 -c32 -s32 -p1 -F1 -B1 -n2 -r4 /dev/nvme0n1 /dev/nvme1n1
> submitter=1, tid=2453, file=/dev/nvme1n1, node=-1
> submitter=0, tid=2452, file=/dev/nvme0n1, node=-1
> polled=1, fixedbufs=1, register_files=1, buffered=0, QD=128
> Engine=io_uring, sq_ring=128, cq_ring=128
> IOPS=10.02M, BW=4.89GiB/s, IOS/call=31/31
> IOPS=10.04M, BW=4.90GiB/s, IOS/call=31/31
> 
> With this:
> taskset -c 2,5 t/io_uring -b512 -d128 -c32 -s32 -p1 -F1 -B1 -n2 -r4 /dev/nvme0n1 /dev/nvme1n1
> submitter=1, tid=2453, file=/dev/nvme1n1, node=-1
> submitter=0, tid=2452, file=/dev/nvme0n1, node=-1
> polled=1, fixedbufs=1, register_files=1, buffered=0, QD=128
> Engine=io_uring, sq_ring=128, cq_ring=128
> IOPS=10.02M, BW=4.89GiB/s, IOS/call=31/31
> IOPS=10.04M, BW=4.90GiB/s, IOS/call=31/31

Not that I don't believe you, but that looks like you pasted the same
stuff in there twice? It's the exact same perf and pids.

-- 
Jens Axboe