Re: [PATCH 4/4] tracing, page-allocator: Add a postprocessing script for page-allocator-related ftrace events

Mel Gorman
2009-08-06T15:54:52Z

On Wed, Aug 05, 2009 at 10:53:50AM -0400, Larry Woodman wrote:
> On Tue, 2009-08-04 at 21:48 +0100, Mel Gorman wrote:
>
> > >
> >
> > Adding and deleting tracepoints, rebuilding and rebooting the kernel is
> > obviously usable by developers but not a whole pile of use if
> > recompiling the kernel is not an option or you're trying to debug a
> > difficult-to-reproduce-but-is-happening-now type of problem.
> >
> > Of the CC list, I believe Larry Woodman has the most experience with
> > these sort of problems in the field so I'm hoping he'll make some sort
> > of comment.
> >
>
> I am all for adding tracepoints that eliminate the need to locate a
> problem, add debug code, rebuild, reboot and retest until the real
> problem is found.
>
> Personally I have not seen as many problems in the page allocator as I
> have in the page reclaim code thats why the majority of my tracepoints
> were in vmscan.c

I'd be surprised if you had, problems in page reclaim would be a lot
more obvious for a start. The page allocator happened to be where I wanted
tracepoints at the moment and I think the next patchset will act as a template
for how to introduce tracepoints which can be repeated for the reclaim points.

> However I do ACK this patch set because it provides
> the opportunity to zoom into the page allocator dynamically without
> needing to iterate through the cumbersome debug process.
>

Thanks.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab