From: Jakub Kicinski <kuba@kernel.org>
To: Samuel Moelius <sam.moelius@trailofbits.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org (open list:TC subsystem),
linux-kernel@vger.kernel.org (open list)
Subject: Re: [PATCH] net/sched: drr: reseed active class deficit after quantum changes
Date: Tue, 9 Jun 2026 18:56:25 -0700 [thread overview]
Message-ID: <20260609185625.6e4bb757@kernel.org> (raw)
In-Reply-To: <20260609003617.1237785.3427a8f0e7b0.drr-change-class-stale-deficit@trailofbits.com>
On Tue, 9 Jun 2026 00:36:18 +0000 Samuel Moelius wrote:
> Subject: [PATCH] net/sched: drr: reseed active class deficit after quantum changes
If the change is not for a serious bug it needs to be generated against
net-next. This was generated against Linus's tree I guess and doesn't
apply to -next.
> Changing the quantum of an active DRR class leaves the old deficit in
> place. The next scheduling round can therefore use credit accumulated
> under a different quantum.
>
> This can be observed by making a class active, changing its quantum, and
> then dequeuing with the old deficit still present.
>
> When an active class quantum changes, reseed its deficit from the new
> quantum so the changed class weight is reflected immediately.
TBH the current implementation is how I would expect DRR to work.
quantum is the "refill" value, it should not reset the state of
the current round? It wouldn't in an ASIC.
--
pw-bot: cr
prev parent reply other threads:[~2026-06-10 1:56 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-09 0:36 [PATCH] net/sched: drr: reseed active class deficit after quantum changes Samuel Moelius
2026-06-10 1:56 ` Jakub Kicinski [this message]
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