Message-ID: <487C6515.1040005@qualcomm.com>
Date: Tue, 15 Jul 2008 01:51:33 -0700
From: Max Krasnyansky <maxk@qualcomm.com>
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To: Rusty Russell <rusty@rustcorp.com.au>
CC: Heiko Carstens <heiko.carstens@de.ibm.com>,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       Christian Borntraeger <borntraeger@de.ibm.com>,
       Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
       linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org,
       Zachary Amsden <zach@vmware.com>
Subject: Re: [PATCH] stopmachine: add stopmachine_timeout
References: <487B05CE.1050508@jp.fujitsu.com> <20080714212026.GA6705@osiris.boeblingen.de.ibm.com> <487C0A76.8060401@qualcomm.com> <200807151810.00365.rusty@rustcorp.com.au>
In-Reply-To: <200807151810.00365.rusty@rustcorp.com.au>
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Rusty Russell wrote:
> On Tuesday 15 July 2008 12:24:54 Max Krasnyansky wrote:
>> Heiko Carstens wrote:
>>> On Mon, Jul 14, 2008 at 11:56:18AM -0700, Jeremy Fitzhardinge wrote:
>>> This is asking for trouble... a config option to disable this would be
>>> nice. But as I don't know which problem this patch originally addresses
>>> it might be that this is needed anyway. So lets see why we need it first.
>> How about this. We'll make this a sysctl, as Rusty already did, and set the
>> default to 0 which means "never timeout". That way crazy people like me who
>> care about this scenario can enable this feature.
> 
> Indeed, this was my thought too.  s390 can initialize it to zero somewhere in 
> their boot code.
> 
>> btw Rusty, I just had this "why didn't I think of that" moments. This is
>> actually another way of handling my workload. I mean it certainly does not
>> fix the root case of the problems and we still need other things that we
>> talked about (non-blocking module delete, lock-free module insertion, etc)
>> but at least in the mean time it avoids wedging the machines for good.
>> btw I'd like that timeout in milliseconds. I think 5 seconds is way tooooo
>> long :).
> 
> We can make it ms, sure.  200ms should be plenty of time: worst I ever saw was 
> 150ms, and that was some weird Power box doing crazy stuff.  I wouldn't be 
> surprised if you'd never see 1ms on your hardware.
Sounds good.

> The ipi idea would handle your case a little more nicely, too, but that's 
> probably not going to hit this merge window.
Which reminds me that I wanted to submit a bunch of kthread and workqueue
related things in this window :).

Max
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