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Tom Lane 01-08-2008 08:28 PM

PPC needs lots more stack space in rawhide??
 
I'm having a tough time trying to get mysql rebuilt in rawhide: the ppc
build keeps failing like this:
http://koji.fedoraproject.org/koji/getfile?taskID=335275&name=build.log

Normally what a failure in execution_constants means is that the
configuration constant STACK_MIN_SIZE has to be increased, because the
error-recovery code needs more stack space than it did before. We have
for years had to run that a bit higher than what mysql.com ships, but up
to now 16384 has worked fine across all arches (all 7 redhat arches,
not just Fedora). Sometime since 13 Dec 2007, however, the behavior
of the ppc arch changed in rawhide, and now even boosting the number
by 50% (to 24K) doesn't persuade it to work. I could try larger
numbers, at the cost of also increasing DEFAULT_THREAD_STACK which
is a pretty user-visible number. I am wondering if this isn't a bug
in rawhide, though. Has gcc started making PPC stack frames a lot
larger than before? Maybe glibc has gotten more stack-hungry? I'd
guess on the problem being in gettext() or related code, if it is a
glibc change, but I haven't tracked it down exactly.

I can't prove at the moment that the problem affects *only* PPC, but
given that that build always dies first it seems pretty likely.

If anyone has a clue what to look at, I'd appreciate it.

regards, tom lane

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David Woodhouse 01-09-2008 09:15 AM

PPC needs lots more stack space in rawhide??
 
On Tue, 2008-01-08 at 16:28 -0500, Tom Lane wrote:
> I'm having a tough time trying to get mysql rebuilt in rawhide: the ppc
> build keeps failing like this:
> http://koji.fedoraproject.org/koji/getfile?taskID=335275&name=build.log
>
> Normally what a failure in execution_constants means is that the
> configuration constant STACK_MIN_SIZE has to be increased, because the
> error-recovery code needs more stack space than it did before. We have
> for years had to run that a bit higher than what mysql.com ships, but up
> to now 16384 has worked fine across all arches (all 7 redhat arches,
> not just Fedora). Sometime since 13 Dec 2007, however, the behavior
> of the ppc arch changed in rawhide, and now even boosting the number
> by 50% (to 24K) doesn't persuade it to work. I could try larger
> numbers, at the cost of also increasing DEFAULT_THREAD_STACK which
> is a pretty user-visible number. I am wondering if this isn't a bug
> in rawhide, though. Has gcc started making PPC stack frames a lot
> larger than before? Maybe glibc has gotten more stack-hungry? I'd
> guess on the problem being in gettext() or related code, if it is a
> glibc change, but I haven't tracked it down exactly.

For a while we used 64KiB pages on ppc64, because IBM insisted on it in
RHEL5 and I didn't notice we'd done the same stupid thing in Fedora. I
believe it was like that in FC6 but I fixed it again for F7.

Is it possible that the kernel on the build machines is now similarly
afflicted?

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Michael Schwendt 01-09-2008 09:23 AM

PPC needs lots more stack space in rawhide??
 
On Wed, 09 Jan 2008 10:15:59 +0000, David Woodhouse wrote:

>
> On Tue, 2008-01-08 at 16:28 -0500, Tom Lane wrote:
> > I'm having a tough time trying to get mysql rebuilt in rawhide: the ppc
> > build keeps failing like this:
> > http://koji.fedoraproject.org/koji/getfile?taskID=335275&name=build.log
> >
> > Normally what a failure in execution_constants means is that the
> > configuration constant STACK_MIN_SIZE has to be increased, because the
> > error-recovery code needs more stack space than it did before. We have
> > for years had to run that a bit higher than what mysql.com ships, but up
> > to now 16384 has worked fine across all arches (all 7 redhat arches,
> > not just Fedora). Sometime since 13 Dec 2007, however, the behavior
> > of the ppc arch changed in rawhide, and now even boosting the number
> > by 50% (to 24K) doesn't persuade it to work. I could try larger
> > numbers, at the cost of also increasing DEFAULT_THREAD_STACK which
> > is a pretty user-visible number. I am wondering if this isn't a bug
> > in rawhide, though. Has gcc started making PPC stack frames a lot
> > larger than before? Maybe glibc has gotten more stack-hungry? I'd
> > guess on the problem being in gettext() or related code, if it is a
> > glibc change, but I haven't tracked it down exactly.
>
> For a while we used 64KiB pages on ppc64, because IBM insisted on it in
> RHEL5 and I didn't notice we'd done the same stupid thing in Fedora. I
> believe it was like that in FC6 but I fixed it again for F7.
>
> Is it possible that the kernel on the build machines is now similarly
> afflicted?

In December the builders have been upgraded to RHEL5.

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Dennis Gilmore 01-09-2008 12:22 PM

PPC needs lots more stack space in rawhide??
 
On Wednesday 09 January 2008, David Woodhouse wrote:
> On Tue, 2008-01-08 at 16:28 -0500, Tom Lane wrote:
> > I'm having a tough time trying to get mysql rebuilt in rawhide: the ppc
> > build keeps failing like this:
> > http://koji.fedoraproject.org/koji/getfile?taskID=335275&name=build.log
> >
> > Normally what a failure in execution_constants means is that the
> > configuration constant STACK_MIN_SIZE has to be increased, because the
> > error-recovery code needs more stack space than it did before. We have
> > for years had to run that a bit higher than what mysql.com ships, but up
> > to now 16384 has worked fine across all arches (all 7 redhat arches,
> > not just Fedora). Sometime since 13 Dec 2007, however, the behavior
> > of the ppc arch changed in rawhide, and now even boosting the number
> > by 50% (to 24K) doesn't persuade it to work. I could try larger
> > numbers, at the cost of also increasing DEFAULT_THREAD_STACK which
> > is a pretty user-visible number. I am wondering if this isn't a bug
> > in rawhide, though. Has gcc started making PPC stack frames a lot
> > larger than before? Maybe glibc has gotten more stack-hungry? I'd
> > guess on the problem being in gettext() or related code, if it is a
> > glibc change, but I haven't tracked it down exactly.
>
> For a while we used 64KiB pages on ppc64, because IBM insisted on it in
> RHEL5 and I didn't notice we'd done the same stupid thing in Fedora. I
> believe it was like that in FC6 but I fixed it again for F7.
>
> Is it possible that the kernel on the build machines is now similarly
> afflicted?

The build system when refreshed in December got updates to RHEL5 so are all
running RHEL5 kernels. they do have one extra patch for a bug in tux.

Dennis
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Tom Lane 01-09-2008 03:11 PM

PPC needs lots more stack space in rawhide??
 
Dennis Gilmore <dennis@ausil.us> writes:
> On Wednesday 09 January 2008, David Woodhouse wrote:
>> On Tue, 2008-01-08 at 16:28 -0500, Tom Lane wrote:
>>> ... Has gcc started making PPC stack frames a lot
>>> larger than before? Maybe glibc has gotten more stack-hungry? I'd
>>> guess on the problem being in gettext() or related code, if it is a
>>> glibc change, but I haven't tracked it down exactly.
>>
>> For a while we used 64KiB pages on ppc64, because IBM insisted on it in
>> RHEL5 and I didn't notice we'd done the same stupid thing in Fedora. I
>> believe it was like that in FC6 but I fixed it again for F7.
>>
>> Is it possible that the kernel on the build machines is now similarly
>> afflicted?

> The build system when refreshed in December got updates to RHEL5 so are all
> running RHEL5 kernels. they do have one extra patch for a bug in tux.

Interesting, but would that affect the rate at which userland code
consumes stack space?

Since posting, I've verified that it still fails at STACK_MIN_SIZE = 48K,
which is 300% of the setting that had worked up through mid-December.
So *something* has gone pretty seriously wacko, but it's hard to tell
what. I guess I shall have to request buildroot access and start poking
at it with a debugger ...

regards, tom lane

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David Woodhouse 01-09-2008 03:22 PM

PPC needs lots more stack space in rawhide??
 
On Wed, 2008-01-09 at 11:11 -0500, Tom Lane wrote:
> Dennis Gilmore <dennis@ausil.us> writes:
> > On Wednesday 09 January 2008, David Woodhouse wrote:
> >> On Tue, 2008-01-08 at 16:28 -0500, Tom Lane wrote:
> >>> ... Has gcc started making PPC stack frames a lot
> >>> larger than before? Maybe glibc has gotten more stack-hungry? I'd
> >>> guess on the problem being in gettext() or related code, if it is a
> >>> glibc change, but I haven't tracked it down exactly.
> >>
> >> For a while we used 64KiB pages on ppc64, because IBM insisted on it in
> >> RHEL5 and I didn't notice we'd done the same stupid thing in Fedora. I
> >> believe it was like that in FC6 but I fixed it again for F7.
> >>
> >> Is it possible that the kernel on the build machines is now similarly
> >> afflicted?
>
> > The build system when refreshed in December got updates to RHEL5 so are all
> > running RHEL5 kernels. they do have one extra patch for a bug in tux.
>
> Interesting, but would that affect the rate at which userland code
> consumes stack space?

It'll certainly affect the way it _allocates_ stack space.

> Since posting, I've verified that it still fails at STACK_MIN_SIZE = 48K,

That's still less than a single page. Did you try 64KiB or 128KiB?

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Tom Lane 01-09-2008 03:46 PM

PPC needs lots more stack space in rawhide??
 
David Woodhouse <dwmw2@infradead.org> writes:
> On Wed, 2008-01-09 at 11:11 -0500, Tom Lane wrote:
>> Interesting, but would that affect the rate at which userland code
>> consumes stack space?

> It'll certainly affect the way it _allocates_ stack space.

>> Since posting, I've verified that it still fails at STACK_MIN_SIZE = 48K,

> That's still less than a single page. Did you try 64KiB or 128KiB?

I think you're missing the context. The actual requested size of the
thread stack is 192K or 256K (and I've also tried 512K, without any
better luck). I could see kernel page size affecting the result of that
allocation request, but all the values are multiples of 64K already.

The problem I'm having is with some code that tries to detect how much
stack space has been consumed, and error out if it's too much, where
"too much" means the requested stack size minus STACK_MIN_SIZE. So that
constant needs to be set large enough to ensure that the error recovery
code itself can execute without overflowing the stack and incurring
SIGSEGV.

My first assumption was that something was using a tad more stack space
than before, but given the latest failed test I'm starting to think that
something's been broken about the stack-depth-testing logic itself.

regards, tom lane

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