Re: [PATCHSET v2 0/7] Improve MSG_RING DEFER_TASKRUN performance

[Pavel Begunkov <asml.silence@gmail.com>]

On 5/30/24 16:23, Jens Axboe wrote:
> Hi,
> 
> For v1 and replies to that and tons of perf measurements, go here:

I'd really prefer the task_work version rather than carving
yet another path specific to msg_ring. Perf might sounds better,
but it's duplicating wake up paths, not integrated with batch
waiting, not clear how affects different workloads with target
locking and would work weird in terms of ordering.

If the swing back is that expensive, another option is to
allocate a new request and let the target ring to deallocate
it once the message is delivered (similar to that overflow
entry).


> https://lore.kernel.org/io-uring/3d553205-0fe2-482e-8d4c-a4a1ad278893@kernel.dk/T/#m12f44c0a9ee40a59b0dcc226e22a0d031903aa73
> 
> as I won't duplicate them in here. Performance has been improved since
> v1 as well, as the slab accounting is gone and we now rely soly on
> the completion_lock on the issuer side.
> 
> Changes since v1:
> - Change commit messages to reflect it's DEFER_TASKRUN, not SINGLE_ISSUER
> - Get rid of the need to double lock on the target uring_lock
> - Relax the check for needing remote posting, and then finally kill it
> - Unify it across ring types
> - Kill (now) unused callback_head in io_msg
> - Add overflow caching to avoid __GFP_ACCOUNT overhead
> - Rebase on current git master with 6.9 and 6.10 fixes pulled in
> 

-- 
Pavel Begunkov