linux-kernel - Re: [PATCHv3] iommu/intel: Ratelimit each dmar fault printing

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Message-ID: <1521129262.2686.23.camel@arista.com>
Date:   Thu, 15 Mar 2018 15:54:22 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     linux-kernel@...r.kernel.org, 0x7f454c46@...il.com,
        Alex Williamson <alex.williamson@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCHv3] iommu/intel: Ratelimit each dmar fault printing

On Thu, 2018-03-15 at 16:28 +0100, Joerg Roedel wrote:
> On Thu, Mar 15, 2018 at 02:42:00PM +0000, Dmitry Safonov wrote:
> > But even with loop-limit we will need ratelimit each printk()
> > *also*.
> > Otherwise loop-limit will be based on time spent printing, not on
> > anything else..
> > The patch makes sense even with loop-limit in my opinion.
> 
> Looks like I mis-read your patch, somehow it looked to me as if you
> replace all 'ratelimited' usages with a call to __ratelimit(), but
> you
> just move 'ratelimited' into the loop, which actually makes sense.

Oh, ok

> But still, this alone is no proper fix for the soft-lockups you are
> seeing.

Well, I can also limit number of loops with say cap_num_fault_regs().
I didn't do that as on my measures the time spent on clearing a fault
is so small, that I'm not sure if it's possible to stuck in this loop.

-- 
Thanks,
             Dmitry