From: Jan Stancek <jstancek@redhat.com>
To: Dave Jones <davej@codemonkey.org.uk>
Cc: trinity@vger.kernel.org
Subject: Re: [bug] child processes stall forever and don't get killed
Date: Fri, 9 Sep 2016 10:16:17 -0400 (EDT) [thread overview]
Message-ID: <907265021.1542338.1473430577178.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <20160909133236.qm32kmsz3wfby53y@codemonkey.org.uk>
----- Original Message -----
> From: "Dave Jones" <davej@codemonkey.org.uk>
> To: "Jan Stancek" <jstancek@redhat.com>
> Cc: trinity@vger.kernel.org
> Sent: Friday, 9 September, 2016 3:32:36 PM
> Subject: Re: [bug] child processes stall forever and don't get killed
>
> On Fri, Sep 09, 2016 at 06:30:16AM -0400, Jan Stancek wrote:
> > Hi,
> >
> > I'm running v1.6-643-gecea2b06d5f3 on RHEL7.3 and I'm seeing an issue
> > where all child processes stall and none of them is getting killed.
> > They are usually in a syscalls like read, recv, nanosleep, etc.
> >
> > I suspect this commit introduced the problem, because any syscall
> > that started but not completed is now considered to "make progress":
> >
> > commit ecf6dfd83d4c886d78d4605163cb8c3f1728db62
> > Author: Dave Jones <davej@codemonkey.org.uk>
> > Date: Fri Aug 12 15:05:01 2016 -0400
> >
> > if we haven't done a syscall yet, treat child as "making progress".
> >
> > Chances are that we haven't been scheduled because some other
> > children are hogging the cpu.
> >
> > I'm seeing more the opposite of what commit above says. Most CPUs
> > are idle, because N-1 children are stuck in recv/read/...
> > and last child manages to keep going. Then by a chance it also hits
> > a syscall that doesn't complete and system stays idle
> > (after ~hour I gave up waiting).
>
> Need to think some more on this, but as a quick guess...
> try replacing the <= BEFORE with < BEFORE
I've started new test with patch above reverted and that looks good
so far. No stalls after 1 hour. Previously it stalled after ~20-30
minutes. I noticed that when syscall stat messages (those which show
number of iteration) stopped appearing.
>
> I'll try and find some time to look into this soon. I'm surprised I
> haven't also seen it happen though. How many CPUs & how many child
> processes ?
Anywhere from 2-8 CPUs, 8-32 children on x86_64, ppc64le and s390x
systems (RHEL7.3 Beta). It happened usually within 20-30 minutes.
Regards,
Jan
>
> Dave
>
>
next prev parent reply other threads:[~2016-09-09 14:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1139550397.1201862.1473415639192.JavaMail.zimbra@redhat.com>
2016-09-09 10:30 ` [bug] child processes stall forever and don't get killed Jan Stancek
2016-09-09 13:32 ` Dave Jones
2016-09-09 14:16 ` Jan Stancek [this message]
2016-09-10 1:46 ` Dave Jones
2016-09-13 12:00 ` Jan Stancek
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