Re: [perfmon2] libpfm syscall patch

[stephane e. <er...@go...>]

Dan,

I must have gotten the wrong syscall base for 2.6.24 on Itanium.

Please send me the value of sys_pfm_create_context in
include/asm-ia64/unistd.h from
your kernel source tree.


On Thu, Apr 3, 2008 at 10:47 PM, Dan Terpstra <ter...@ee...> wrote:
> We tried again with an unpatched libpfm and got a Bad File Descriptor error
>  message. At least it looks like it's getting into the kernel now. Any clues?
>
>  terpstra@anaka:~> uname -a
>  Linux anaka 2.6.24-perfmon2 #2 SMP Tue Apr 1 14:06:29 EDT 2008 ia64 ia64
>  ia64 GNU/Linux
>
>  - d
>
>
>  > -----Original Message-----
>  > From: Dan Terpstra [mailto:ter...@ee...]
>  > Sent: Thursday, April 03, 2008 4:40 PM
>  > To: 'stephane eranian'; 'per...@li...'
>  > Subject: RE: [perfmon2] libpfm syscall patch
>  >
>  > Stephane -
>  > We applied your patch to a fresh checkout of libpfm and tried it on our
>  > newly patched Montecito. It failed with a "function not implemented" error
>  > on a call to pfm_create_context. I'm guessing there needs to be a separate
>  > case in the switch for Montecito. I only saw a generic __ia64__
>  > We'll try again with an unpatched fresh copy of libpfm.
>  > - dan
>  >
>  > > -----Original Message-----
>  > > From: per...@li... [mailto:perfmon2-
>  > devel-
>  > > bo...@li...] On Behalf Of stephane eranian
>  > > Sent: Thursday, April 03, 2008 10:12 AM
>  > > To: per...@li...
>  > > Subject: [perfmon2] libpfm syscall patch
>  > >
>
>
> > > Hello,
>  > >
>  > > I got tired of having to maintain different revisions for libpfm, one
>  > > each time the perfmon syscalls
>  > > change. Sometimes back ward compatibility is not possible because the
>  > > perfmon API/ABI changed.
>  > > But nowadays, changes are happening inside the kernel not so much at
>  > > the user level.
>  > >
>  > > There have been several new system calls in recent kernels. Those push
>  > > the perfmon syscalls up
>  > > on every architectures.
>  > >
>  > > Libpfm provides the syscall stubs to call the kernel perfmon API.
>  > > Those stubs will eventually migrate
>  > > into libc. The syscall numbers were kept in include/perfmon/perfmon.h
>  > > and had to be updated for each
>  > > new kernel version. The problem is that backward compatibility
>  > > (whenever possible) was not provided.
>  > >
>  > > I have created the attached patch to address this problem. The same
>  > > libpfm can now be used between
>  > > kernel revisions as long as the perfmon API does not change. This is,
>  > > for instance, the case between
>  > > 2.6.24 and 2.6.25 for instance. The trick is to have the code
>  > > autodetect the kernel version and adjust
>  > > the syscall accordingly. Another solution would have been to have the
>  > > kernel export the base syscall
>  > > number via, let's say, /sys/kernel/perfmon/syscall.
>  > >
>  > > I am still hoping we will be in mainline soon, or at least that we
>  > > will get a fixed block of syscalls soon,
>  > > at which point, all of this will not be needed anymore, except for
>  > > special platforms such as Cray.
>  > >
>  > > I have tested the attached patch on 2.6.25 on X86-64, i386. Please
>  > > test it on your platforms and
>  > > report any problem.
>  > >
>  > > Thanks.
>
>