From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752392AbeCOOey (ORCPT ); Thu, 15 Mar 2018 10:34:54 -0400 Received: from mail-wm0-f52.google.com ([74.125.82.52]:50660 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752108AbeCOOex (ORCPT ); Thu, 15 Mar 2018 10:34:53 -0400 X-Google-Smtp-Source: AG47ELsZqC4JWP7UowjqRGDCY6wdACcRGAIJZNK0iZZAJq4Ru8SPpMPFXXD1B/5Wlu6S5HtqPAzIvQ== Message-ID: <1521124490.2686.16.camel@arista.com> Subject: Re: [PATCHv3] iommu/intel: Ratelimit each dmar fault printing From: Dmitry Safonov To: Joerg Roedel Cc: linux-kernel@vger.kernel.org, 0x7f454c46@gmail.com, Alex Williamson , David Woodhouse , Ingo Molnar , Lu Baolu , iommu@lists.linux-foundation.org Date: Thu, 15 Mar 2018 14:34:50 +0000 In-Reply-To: <20180315142253.GC5259@8bytes.org> References: <20180215191729.15777-1-dima@arista.com> <20180315134649.skh2aukcmg5ud74y@8bytes.org> <1521123183.2686.7.camel@arista.com> <20180315142253.GC5259@8bytes.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.24.6 (3.24.6-1.fc26) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2018-03-15 at 15:22 +0100, Joerg Roedel wrote: > On Thu, Mar 15, 2018 at 02:13:03PM +0000, Dmitry Safonov wrote: > > So, you suggest to remove ratelimit at all? > > Do we really need printk flood for each happened fault? > > Imagine, you've hundreds of mappings and then PCI link flapped.. > > Wouldn't it be better to keep ratelimiting? > > I don't mind, just it looks a bit strange to me. > > I never said you should remove the ratelimiting, after all you are > trying to fix a soft-lockup, no? > > And that should not be fixed by changes to the ratelimiting, but with > proper irq handling. Uh, I'm a bit confused then. - Isn't it better to ratelimit each printk() instead of bunch of printks inside irq handler? - I can limit the number of loops, but the most of the time is spent in the loop on printk() (on my machine ~170msec per loop), while everything else takes much lesser time (on my machine < 1 usec per loop). So, if I will limit number of loops per-irq, that cycle-limit will be based on limiting time spent on printk (e.g., how many printks to do in atomic context so that node will not lockup). It smells like ratelimiting, no? I must be misunderstanding something, but why introducing another limit for number of printk() called when there is ratelimit which may be tuned.. -- Thanks, Dmitry