From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753591AbcHQFRF (ORCPT ); Wed, 17 Aug 2016 01:17:05 -0400 Received: from helcar.hengli.com.au ([209.40.204.226]:46269 "EHLO helcar.hengli.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752003AbcHQFRE (ORCPT ); Wed, 17 Aug 2016 01:17:04 -0400 Date: Wed, 17 Aug 2016 13:16:50 +0800 From: Herbert Xu To: Andy Lutomirski Cc: mingo@kernel.org, brgerst@gmail.com, torvalds@linux-foundation.org, x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, dvlasenk@redhat.com, bp@suse.de, tglx@linutronix.de, jpoimboe@redhat.com Subject: Re: [PATCH v3 0/7] x86: Rewrite switch_to() Message-ID: <20160817051650.GA1581@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Core X-Newsgroups: apana.lists.os.linux.kernel User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Lutomirski wrote: > > I will be quite surprised if you can measure any effect at all. I've > never seen context switches take fewer than ~2k cycles, and on my > laptop, they take 8k-9k cycles. The scheduler is really, really slow. Indeed, I think I still have a bugzilla entry somewhere regarding the huge performance regression when we first switched over to the current scheduler. Over the years people have been trying to hack around it, e.g., network driver polling, low latency socket, anything to avoid going into the scheduler. We really should fix it properly some day. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt