From: Stefan Hajnoczi <stefanha@redhat.com>
To: Jaehoon Kim <jhkim@linux.ibm.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org,
mjrosato@linux.ibm.com, farman@linux.ibm.com,
pbonzini@redhat.com, fam@euphon.net, armbru@redhat.com,
eblake@redhat.com, berrange@redhat.com, eduardo@habkost.net,
dave@treblig.org, sw@weilnetz.de
Subject: Re: [PATCH RFC v2 1/3] aio-poll: avoid unnecessary polling time computation
Date: Wed, 25 Mar 2026 13:22:36 -0400 [thread overview]
Message-ID: <20260325172236.GC701300@fedora> (raw)
In-Reply-To: <20260323135451.579655-2-jhkim@linux.ibm.com>
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On Mon, Mar 23, 2026 at 08:54:49AM -0500, Jaehoon Kim wrote:
> Nodes are no longer added to poll_aio_handlers when adaptive polling is
> disabled, preventing unnecessary try_poll_mode() calls. Additionally,
> aio_poll() skips try_poll_mode() when timeout is 0.
Skipping when timeout is 0 seems risky to me. VIRTIO devices disable
guest kicks when polling mode is started. When aio_poll(ctx,
blocking=false) is called, we will skip polling and
ctx->fdmon_ops->need_wait(ctx) won't detect an event either. aio_poll()
will return without noticing that the VIRTIO device's AioHandler is
ready.
Is skipping when timeout 0 necessary for performance or can it be
dropped from the patch?
Aside from this:
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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next prev parent reply other threads:[~2026-03-25 17:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-23 13:54 [PATCH RFC v2 0/3] improve aio-polling efficiency Jaehoon Kim
2026-03-23 13:54 ` [PATCH RFC v2 1/3] aio-poll: avoid unnecessary polling time computation Jaehoon Kim
2026-03-25 17:22 ` Stefan Hajnoczi [this message]
2026-03-23 13:54 ` [PATCH RFC v2 2/3] aio-poll: refine iothread polling using weighted handler intervals Jaehoon Kim
2026-03-25 20:37 ` Stefan Hajnoczi
2026-03-23 13:54 ` [PATCH RFC v2 3/3] qapi/iothread: introduce poll-weight parameter for aio-poll Jaehoon Kim
2026-03-25 14:04 ` Markus Armbruster
2026-03-25 16:52 ` Stefan Hajnoczi
2026-03-25 16:56 ` Stefan Hajnoczi
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