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From: Jens Axboe <[email protected]>
To: Jakub Kicinski <[email protected]>
Cc: Stefan Roesch <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected]
Subject: Re: [RFC PATCH v3 0/3] io_uring: add napi busy polling support
Date: Wed, 16 Nov 2022 13:12:11 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 11/16/22 1:09 PM, Jakub Kicinski wrote:
> On Wed, 16 Nov 2022 11:44:38 -0700 Jens Axboe wrote:
>> Thanks Jakub! Question on the need for patch 3, which I think came about
>> because of comments from you. Can you expand on why we need both an
>> enable and timeout setting? Are there cases where timeout == 0 and
>> enabled == true make sense?
> 
> The enable is for the "prefer busy poll" mode, rather that just busy
> polling.
> 
> The prefer busy poll mode disables interrupts and arms a (hopefully
> long enough) fail safe timer, and expects user to come back and busy
> poll before the timer fires. The timer length is set thru sysfs params
> for NAPI/queue.
> 
> Because the Rx traffic is fully async and not in control of the local
> app, this gives the local app the ability to postpone the Rx IRQ.
> No interruptions means lower response latency. 
> With the expectation that the app will read/"busy poll" next batch of
> packets once its done servicing the previous batch.
> 
> We don't have to implement this bit from the start, "normal" busy poll
> is already functional with patches 1 and 2.

Gotcha, ok makes sense to me. I'm fine with the patchset, just want
a few adjustments on the API side as per previous email. I think
Stefan is respinning with that, then we can get it queued up.

-- 
Jens Axboe



      reply	other threads:[~2022-11-16 20:12 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-15  7:08 [RFC PATCH v3 0/3] io_uring: add napi busy polling support Stefan Roesch
2022-11-15  7:08 ` [RFC PATCH v3 1/3] " Stefan Roesch
2022-11-15  7:08 ` [RFC PATCH v3 2/3] io_uring: add api to set napi busy poll timeout Stefan Roesch
2022-11-16 19:05   ` Jens Axboe
2022-11-15  7:09 ` [RFC PATCH v3 3/3] io_uring: add api to set napi prefer busy poll Stefan Roesch
2022-11-16 18:31 ` [RFC PATCH v3 0/3] io_uring: add napi busy polling support Jakub Kicinski
2022-11-16 18:44   ` Jens Axboe
2022-11-16 20:09     ` Jakub Kicinski
2022-11-16 20:12       ` Jens Axboe [this message]

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