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[81.185.160.72]) by smtp.gmail.com with ESMTPSA id h16sm26925802wrv.88.2019.07.18.08.08.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 08:08:22 -0700 (PDT) Subject: Re: regression with napi/softirq ? To: Sudip Mukherjee , Eric Dumazet Cc: Thomas Gleixner , "Peter Zijlstra (Intel)" , "David S. Miller" , netdev , linux-kernel References: <20190717201925.fur57qfs2x3ha6aq@debian> <052e43b6-26f8-3e46-784e-dc3c6a82bdf0@gmail.com> <8124bbe5-eaa8-2106-2695-4788ec0f6544@gmail.com> From: Eric Dumazet Message-ID: <870de0d9-5c08-9431-a46a-33ee4d3a6617@gmail.com> Date: Thu, 18 Jul 2019 17:08:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/18/19 2:55 PM, Sudip Mukherjee wrote: > Thanks Eric. But there is no improvement in delay between > softirq_raise and softirq_entry with this change. > But moving to a later kernel (linus master branch? ) like Thomas has > said in the other mail might be difficult atm. I can definitely > move to v4.14.133 if that helps. Thomas ? If you are tracking max latency then I guess you have to tweak SOFTIRQ_NOW_MASK to include NET_RX_SOFTIRQ The patch I gave earlier would only lower the probability of events, not completely get rid of them. diff --git a/kernel/softirq.c b/kernel/softirq.c index 0427a86743a46b7e1891f7b6c1ff585a8a1695f5..302046dd8d7e6740e466c422954f22565fe19e69 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -81,7 +81,7 @@ static void wakeup_softirqd(void) * right now. Let ksoftirqd handle this at its own rate, to get fairness, * unless we're doing some of the synchronous softirqs. */ -#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ)) +#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ) | (1 << NET_RX_SOFTIRQ)) static bool ksoftirqd_running(unsigned long pending) { struct task_struct *tsk = __this_cpu_read(ksoftirqd);