From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id C41316B0078 for ; Mon, 23 Nov 2009 10:34:19 -0500 (EST) Subject: Re: [PATCH v2 10/12] Maintain preemptability count even for !CONFIG_PREEMPT kernels From: Peter Zijlstra In-Reply-To: <1258985167-29178-11-git-send-email-gleb@redhat.com> References: <1258985167-29178-1-git-send-email-gleb@redhat.com> <1258985167-29178-11-git-send-email-gleb@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 23 Nov 2009 16:34:15 +0100 Message-ID: <1258990455.4531.594.camel@laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Gleb Natapov Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, avi@redhat.com, mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, riel@redhat.com List-ID: On Mon, 2009-11-23 at 16:06 +0200, Gleb Natapov wrote: > Do not preempt kernel. Just maintain counter to know if task can be rescheduled. > Asynchronous page fault may be delivered while spinlock is held or current > process can't be preempted for other reasons. KVM uses preempt_count() to check if preemptions is allowed and schedule other process if possible. This works > with preemptable kernels since they maintain accurate information about > preemptability in preempt_count. This patch make non-preemptable kernel > maintain accurate information in preempt_count too. I'm thinking you're going to have to convince some people this won't slow them down for no good. Personally I always have PREEMPT=y, but other people seem to feel strongly about not doing so. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org