linux-kernel - Re: [PATCH 6/8] net: tcp: tsq: Convert from tasklet to BH workqueue

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Message-ID: <CAL+tcoCjaq=CxXdFtCqF4LdwCfenrHi7Nu-XHm+u--phuoC+EA@mail.gmail.com>
Date: Wed, 28 May 2025 07:43:16 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Tejun Heo <tj@...nel.org>
Cc: torvalds@...ux-foundation.org, mpatocka@...hat.com, 
	linux-kernel@...r.kernel.org, dm-devel@...ts.linux.dev, msnitzer@...hat.com, 
	ignat@...udflare.com, damien.lemoal@....com, bob.liu@...cle.com, 
	houtao1@...wei.com, peterz@...radead.org, mingo@...nel.org, 
	netdev@...r.kernel.org, allen.lkml@...il.com, kernel-team@...a.com, 
	Eric Dumazet <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	David Ahern <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH 6/8] net: tcp: tsq: Convert from tasklet to BH workqueue

On Wed, May 28, 2025 at 2:55 AM Tejun Heo <tj@...nel.org> wrote:
>
> Hello,
>
> On Sun, May 25, 2025 at 11:51:55AM +0800, Jason Xing wrote:
> > Sorry to revive the old thread! I noticed this change because I've
> > been doing an investigation around TSQ recently. I'm very cautious
> > about the change in the core/sensitive part of the networking area
> > because it might affect some corner cases beyond our limited test,
> > even though I've tested many rounds and no regression results
> > (including the latency between tcp_wfree and tcp_tsq_handler) show up.
> > My main concern is what the exact benefit/improvement it could bring
> > with the change applied since your BH workqueue commit[1] says the
> > tasklet mechanism has some flaws. I'd like to see if I can
> > reproduce/verify it.
>
> There won't be any behavioral benefits. It's mostly that it'd be great to
> get rid of tasklets with something which is more generic, so if BH workqueue
> doesn't regress, we want to keep moving users to BH workqueue until all
> tasklet users are gone and then remove tasklet.

I see. So far I haven't see any side effect especially with testing
bulk transfer/multi-thread transfer, so if you're willing to repost it
after the merge window, please feel free to add:

Reviewed-by: Jason Xing <kerneljasonxing@...il.com>

Thanks,
Jason