linux-kernel - Re: [PATCHSET v3 0/5] Add support for epoll min

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Date:   Mon, 7 Nov 2022 15:56:01 -0500
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     axboe@...nel.dk
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCHSET v3 0/5] Add support for epoll min_wait

Hi Jens,
NICs and storage controllers have interrupt mitigation/coalescing
mechanisms that are similar.

NVMe has an Aggregation Time (timeout) and an Aggregation Threshold
(counter) value. When a completion occurs, the device waits until the
timeout or until the completion counter value is reached.

If I've read the code correctly, min_wait is computed at the beginning
of epoll_wait(2). NVMe's Aggregation Time is computed from the first
completion.

It makes me wonder which approach is more useful for applications. With
the Aggregation Time approach applications can control how much extra
latency is added. What do you think about that approach?

Stefan

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