From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752352AbZGXKVs (ORCPT ); Fri, 24 Jul 2009 06:21:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751921AbZGXKVs (ORCPT ); Fri, 24 Jul 2009 06:21:48 -0400 Received: from smtp-outbound-2.vmware.com ([65.115.85.73]:57522 "EHLO smtp-outbound-2.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751787AbZGXKVr (ORCPT ); Fri, 24 Jul 2009 06:21:47 -0400 Message-ID: <4A698B3E.4020208@vmware.com> Date: Fri, 24 Jul 2009 12:21:50 +0200 From: Thomas Hellstrom User-Agent: Thunderbird 1.5.0.7 (X11/20060921) MIME-Version: 1.0 To: Andi Kleen CC: "linux-kernel@vger.kernel.org" , "mingo@elte.hu" , "venkatesh.pallipadi@intel.com" Subject: Re: [PATCH] x86: Use clflush() instead of wbinvd() whenever possible when changing mapping References: <1248421981-31865-1-git-send-email-thellstrom@vmware.com> <87ocra1jn6.fsf@basil.nowhere.org> In-Reply-To: <87ocra1jn6.fsf@basil.nowhere.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen wrote: > Thomas Hellstrom writes: > > >> The current code uses wbinvd() when the area to flush is > 4MB. Although this >> may be faster than using clflush() the effect of wbinvd() on irq latencies >> may be catastrophical on systems with large caches. Therefore use clflush() >> > > may be? You seem to miss some hard data here. > > Admittedly. However, the concept of flushing and invalidating the caches completely on systems with many processors and huge caches when we intend to only flush only small piece of the cache also sounds like a big overkill. Furthermore, since the wbinvd() has been introduced as an optimization of the general clflush() case, did somebody ever check the effects on systems with many processors and huge caches? /Thomas > -Andi > >