linux-kernel - RE: [????] Re: [PATCH net-next] netfilter: conntrack: Reduce cond_resched frequency in gc

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Message-ID: <13de94827815469193e10d6fb0c0d45b@baidu.com>
Date: Wed, 15 Oct 2025 01:56:35 +0000
From: "Li,Rongqing" <lirongqing@...du.com>
To: Florian Westphal <fw@...len.de>
CC: Pablo Neira Ayuso <pablo@...filter.org>, Jozsef Kadlecsik
	<kadlec@...filter.org>, Phil Sutter <phil@....cc>, "David S . Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
	<horms@...nel.org>, "netfilter-devel@...r.kernel.org"
	<netfilter-devel@...r.kernel.org>, "coreteam@...filter.org"
	<coreteam@...filter.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [????] Re: [PATCH net-next] netfilter: conntrack: Reduce
 cond_resched frequency in gc_worker

> > The current implementation calls cond_resched() in every iteration of
> > the garbage collection loop. This creates some overhead when
> > processing large conntrack tables with billions of entries, as each
> > cond_resched() invocation involves scheduler operations.
> >
> > To reduce this overhead, implement a time-based throttling mechanism
> > that calls cond_resched() at most once per millisecond. This maintains
> > system responsiveness while minimizing scheduler contention.
> >
> > gc_worker() with hashsize=10000 shows measurable improvement:
> >
> > Before: 7114.274us
> > After:  5993.518us (15.8% reduction)
> 
> I dislike this, I have never seen this pattern.
> 

This patch is similar as 

commit 271557de7cbfdecb08e89ae1ca74647ceb57224f
    xfs: reduce the rate of cond_resched calls inside scrub

> Whole point of cond_resched() is to let scheduler decide.
> 
> Maybe it would be better to move gc_worker off to its own work queue
> (create_workqueue()) instead of reusing system wq so one can tune the
> priority instead?

I am fine to move gc_worker to its own work queue

Thanks

-Li