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Date: Sun, 04 Dec 2011 15:22:53 -0500
From: Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
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Subject: Re: Machine very sluggish while compiling
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Trying again without the verboten 80kB PNG attachment...

On 04/12/2011 3:18 PM, Ryan Johnson wrote:
> On 04/12/2011 2:29 PM, Christopher Faylor wrote:
>> On Sun, Dec 04, 2011 at 02:55:13AM -0500, Ryan Johnson wrote:
>>> On 25/11/2011 10:47 AM, Spiro Trikaliotis wrote:
>>>> Hello,
>>>>
>>>> * On Thu, Nov 24, 2011 at 07:59:58PM -0500 Ryan Johnson wrote:
>>>>
>>>>> Lately I've noticed that running make -j4 on my quad-core win7-x64
>>>>> machine causes it to become sluggish or even unresponsive.
>>>> I have seen very similar effects on my Win7-64 box. I can force the
>>>> problem here just be running "ccrypt", though, I do not need to use 
>>>> "make
>>>> -j4".
>>>>
>>>> I assume it has to do with the Windows 64 bit problems of Cygwin 
>>>> (search
>>>> the ML archives for that).
>>>>
>>>> For me, this is the first machine since years where I do not use 
>>>> Cygwin
>>>> because of this issue.
>>> Update: I hit the problem again, this time running python, and the
>>> problem is repeatable with the native 64-bit windows python 
>>> interpreter.
>>> It looks like cygwin doesn't cause the problem, but rather my high-cpu
>>> tasks tend to run under cygwin. Honestly, I wouldn't expect cygwin 
>>> to be
>>> the cause, given that it's a user space only piece of software!
>>>
>>> Now what other entity could be the cause, I haven't a clue... process
>>> explorer doesn't show anything. Maybe that's because it's frozen along
>>> with the rest of the world during these episodes; right as it comes 
>>> back
>>> I see context switch deltas above 100k for the interrupt/DPC module,
>>> which suggests I've got a wonky driver somewhere.
>> Out of curiousity, is the current snapshot any better?  I just found a
>> case where Cygwin could essentially enter a tight loop while waiting for
>> I/O.  It would seem to be working correctly but it would use a lot of
>> CPU time.
> Again, I'm no longer convinced that this is Cygwin's fault -- it just 
> so happened that all my CPU-intensive tasks were cygwin apps. I'm 
> starting to notice a pattern, though: with three cpu-bound apps 
> running, my laptop's fan comes on every two minutes (precisely). About 
> five seconds later, the frequency drops by 50% and cpu util promptly 
> saturates as a result. After one minute of this, the frequency hikes 
> back up and we're good... until the cycle repeats a minute later (see 
> the attached snippet of screen shot).
>
> So, the questions are how come:
> - power/heat management isn't giving the fan a chance to work before 
> clamping the clock frequency?
> - scheduler can't cope better with 100% cpu util?
>
> While I'm glad to take any expert advice people might have, I think we 
> can close this thread as far as Cygwin is concerned.
>
> BTW, Corinna's advice to disable PCA did help somewhat (and 
> Firefox/Thunderbird util dropped as well as a bonus). However, it's 
> probably only a treatment of symptoms in my case; I already had 
> superfetch disabled.
>
> Thanks,
> Ryan
>


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