On Fri, Aug 05, 2022 at 12:15:24PM -0600, Jens Axboe wrote:
On 8/5/22 12:11 PM, Keith Busch wrote:
On Fri, Aug 05, 2022 at 11:18:38AM -0600, Jens Axboe wrote:
On 8/5/22 11:04 AM, Jens Axboe wrote:
On 8/5/22 9:42 AM, Kanchan Joshi wrote:
Hi,
Series enables async polling on io_uring command, and nvme passthrough
(for io-commands) is wired up to leverage that.
512b randread performance (KIOP) below:
QD_batch block passthru passthru-poll block-poll
1_1 80 81 158 157
8_2 406 470 680 700
16_4 620 656 931 920
128_32 879 1056 1120 1132
Curious on why passthru is slower than block-poll? Are we missing
something here?
I took a quick peek, running it here. List of items making it slower:
- No fixedbufs support for passthru, each each request will go through
get_user_pages() and put_pages() on completion. This is about a 10%
change for me, by itself.
Enabling fixed buffer support through here looks like it will take a
little bit of work. The driver needs an opcode or flag to tell it the
user address is a fixed buffer, and io_uring needs to export its
registered buffer for a driver like nvme to get to.
Yeah, it's not a straight forward thing. But if this will be used with
recycled buffers, then it'll definitely be worthwhile to look into.
Had posted bio-cache and fixedbufs in the initial round but retracted
to get the foundation settled first.
https://lore.kernel.org/linux-nvme/20220308152105.309618-1-joshi.k@xxxxxxxxxxx/
I see that you brought back bio-cache already. I can refresh fixedbufs.
Completion-batching seems too tightly coupled to block-path.
