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Re: ipvs_syncmaster brings cpu to 100%

To: Roger Tsang <roger.tsang@xxxxxxxxx>, Luca Maranzano <liuk001@xxxxxxxxx>, "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>, Dave Miller <davem@xxxxxxxxxxxxx>, Wensong Zhang <wensong@xxxxxxxxxxxx>, Julian Anastasov <ja@xxxxxx>, netdev@xxxxxxxxxxx
Subject: Re: ipvs_syncmaster brings cpu to 100%
From: Nishanth Aravamudan <nacc@xxxxxxxxxx>
Date: Mon, 26 Sep 2005 06:11:04 -0700
In-reply-to: <20050926081229.GA23755@xxxxxxxxxxxx>
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On 26.09.2005 [17:12:32 +0900], Horms wrote:
> On Mon, Sep 26, 2005 at 05:05:10PM +0900, Horms wrote:
> 
> [snip]
> 
> > > > > > Furthermore, if I make an "rgrep" in the source tree of kernel 
> > > > > > 2.6.12
> > > > > > the function schedule_timeout() is more used than the ssleep() (517
> > > > > > occurrencies vs. 43), so why in ip_vs_sync.c there was this change?
> > > > > >
> > > > > > The other oddity is that Horms reported on this list that on non 
> > > > > > Xeon
> > > > > > CPU the same version of kernel of mine does not present the problem.
> > > > > >
> > > > > > I'm getting crazy :-)
> > > > 
> > > > I've prepared a patch, which reverts the change which was introduced
> > > > by Nishanth Aravamudan in February.
> > > 
> > > Was the 100% cpu utilization only occurring on Xeon processors?
> > 
> > That seems to be the only case where were this problem has been
> > observed. I don't have such a processor myself, so I haven't actually
> > been able to produce the problem locally.
> > 
> > One reason I posted this issue to netdev was to get some more
> > eyes on the problem as it is puzzling to say the least.
> > 
> > > Care to try to use msleep_interruptible() instead of ssleep(), as
> > > opposed to schedule_timeout()?
> > 
> > I will send a version that does that shortly, Luca, can
> > you plase check that too?
> 
> Here is that version of the patch. Nishanth, I take it that I do not
> need to set TASK_INTERRUPTABLE before calling msleep_interruptible(),
> please let me know if I am wrong.

Yes, exactly. I'm just trying to narrow it down to see if it's the task
state that's causing the issue (which, to be honest, doesn't make a lot
of sense to me -- with ssleep() your load average will go up as the task
will be UNINTERRUPTIBLE state, but I am not sure why utilisation would
rise, as you are still sleeping...)

Thanks,
Nish

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