[PATCH, RFC] xfs: event tracing support

[Felix Blyakher]

On Jun 22, 2009, at 3:59 PM, Christoph Hellwig wrote:

> On Mon, Jun 22, 2009 at 01:01:35PM -0500, Felix Blyakher wrote:
>>> To use it make sure CONFIG_EVENT_TRACING is enabled and then enable
>>> all
>>> xfs trace channels by:
>>>
>>>  echo 1 > /sys/kernel/debug/tracing/events/xfs/enable
>>
>> Does event tracing work on ia64 platform?
>> I spent some time on it over weekend, but was not able even
>> to force "CONFIG_EVENT_TRACING=y" setting in the .config.
>> Seems to build ok on x86_64, which does have CONFIG_TRACING
>> in defconfig, and allows to set CONFIG_EVENT_TRACING.
>
> IA64 ftrace support was added earlier this year, but it seems it can't
> be enabled anymore since the big config option reshuffle.  Now tracing
> support requires the architecture to define the TRACE_IRQFLAGS_SUPPORT
> and STACKTRACE_SUPPORT symbols, which seems to be missing on ia64.

That's what I found.
What would it take to add ftrace support on IA64?

>> If tracing is not available on all platforms, especially
>> on ia64, which is one of preferred platforms at SGI, we need
>> to preserve the original XFS tracing facilities. I know, it'll
>> be PIA to keep both tracing methods, but we can't drop
>> the working feature without good replacement.
>
> It's not working at all in mainline and never had.  And for about
> a year thaere hasn't been any tree around that actuall supports it..

True. But with simple patch (basically restoring xfsidbg.c) and
adding kdb support I was using xfs trace successfully. I know,
it doesn't help much if it's not in the mainline, but it's
real working code. Btw, that helped me recently identify the
deadlock in xfs_growfs (xfs qa test 104). I'll post those to
the xfs list or bugzilla shortly.

I hope tracing support for ia64 could be added, and this
issue won't be a showstopper.

Thanks,
Felix