From mboxrd@z Thu Jan 1 00:00:00 1970 From: Qin Chuanyu Subject: What's the concern about setting irq thread's policy as SCHED_FIFO Date: Wed, 3 Dec 2014 16:06:59 +0800 Message-ID: <547EC4A3.6060408@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: To: Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org I am doing network performance test under suse11sp3 and intel 82599 nic, Becasuse the softirq is out of schedule policy's control, so netserver thread couldn't always get 100% cpu usage, then packet dropped in kernel udp socket's receive queue. In order to get a stable result, I did some patch in ixgbe driver and then use irq_thread instead of softirq to handle rx. It seems work well, but irq_thread's SCHED_FIFO schedule policy cause that when the cpu is limited, netserver couldn't work at all. So I change the irq_thread's schedule policy from SCHED_FIFO to SCHED_NORMAL, then the irq_thread could share the cpu usage with netserver thread. the question is: What's the concrete reason about setting irq thread's policy as SCHED_FIFO? Except the priority affecting the cpu usage, any function would be broken if irq thread change to SCHED_NORMAL?