From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: [patch 1/4] - Potential performance bottleneck for Linxu TCP Date: Thu, 30 Nov 2006 13:22:06 +0300 Message-ID: <20061130102205.GA20654@2ka.mipt.ru> References: <20061130061758.GA2003@elte.hu> <20061129.223055.05159325.davem@davemloft.net> <20061130064758.GD2003@elte.hu> <20061129.231258.65649383.davem@davemloft.net> <20061130073504.GA19437@elte.hu> <20061130095232.GA8990@2ka.mipt.ru> <456EAD6E.6040709@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Cc: Ingo Molnar , David Miller , wenji@fnal.gov, akpm@osdl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Received: from relay.2ka.mipt.ru ([194.85.82.65]:24792 "EHLO 2ka.mipt.ru") by vger.kernel.org with ESMTP id S933956AbWK3KWU (ORCPT ); Thu, 30 Nov 2006 05:22:20 -0500 To: Nick Piggin Content-Disposition: inline In-Reply-To: <456EAD6E.6040709@yahoo.com.au> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Nov 30, 2006 at 09:07:42PM +1100, Nick Piggin (nickpiggin@yahoo.com.au) wrote: > >Doesn't the provided solution is just a in-kernel variant of the > >SCHED_FIFO set from userspace? Why kernel should be able to mark some > >users as having higher priority? > >What if workload of the system is targeted to not the maximum TCP > >performance, but maximum other-task performance, which will be broken > >with provided patch. > > David's line of thinking for a solution sounds better to me. This patch > does not prevent the process from being preempted (for potentially a long > time), by any means. It steals timeslices from other processes to complete tcp_recvmsg() task, and only when it does it for too long, it will be preempted. Processing backlog queue on behalf of need_resched() will break fairness too - processing itself can take a lot of time, so process can be scheduled away in that part too. > -- > SUSE Labs, Novell Inc. > Send instant messages to your online friends http://au.messenger.yahoo.com -- Evgeniy Polyakov