Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <202212050936120314474@zte.com.cn> <20221205175354.3949c6bb@kernel.org>
In-Reply-To: <20221205175354.3949c6bb@kernel.org>
From:   Eric Dumazet <edumazet@google.com>
Date:   Tue, 6 Dec 2022 04:18:07 +0100
Message-ID: <CANn89iK4Cn-+BgJEuGSWF=PTfDPWuCy8ci75664+98ajt_+3Xw@mail.gmail.com>
Subject: Re: [PATCH linux-next v2] net: record times of netdev_budget exhausted
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     yang.yang29@zte.com.cn, davem@davemloft.net, pabeni@redhat.com,
        bigeasy@linutronix.de, imagedong@tencent.com, kuniyu@amazon.com,
        petrm@nvidia.com, liu3101@purdue.edu, wujianguo@chinatelecom.cn,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, Dec 6, 2022 at 2:53 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Mon, 5 Dec 2022 09:36:12 +0800 (CST) yang.yang29@zte.com.cn wrote:
> > A long time ago time_squeeze was used to only record netdev_budget
> > exhausted[1]. Then we added netdev_budget_usecs to enable softirq
> > tuning[2]. And when polling elapsed netdev_budget_usecs, it's also
> > record by time_squeeze.
> > For tuning netdev_budget and netdev_budget_usecs respectively, we'd
> > better distinguish from netdev_budget exhausted and netdev_budget_usecs
> > elapsed, so add budget_exhaust to record netdev_budget exhausted.
> >
> > [1] commit 1da177e4c3f4("Linux-2.6.12-rc2")
> > [2] commit 7acf8a1e8a28("Replace 2 jiffies with sysctl netdev_budget_usecs to enable softirq tuning")
>
> Same comments as on v1.

Yes, and if we really want to track all these kinds of events the
break caused by need_resched() in do_softirq would
also need some monitoring.

I feel that more granular tracing (did I say tracepoints) would be more useful.