Messages in this thread | | | Date | Tue, 28 Apr 2009 17:36:08 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags |
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On Tue, Apr 28, 2009 at 05:25:06PM +0800, Pekka Enberg wrote: > On Tue, 2009-04-28 at 09:40 +0200, Andi Kleen wrote: > >>> > > I think i have to NAK this kind of ad-hoc instrumentation of kernel > >>> > > internals and statistics until we clear up why such instrumentation > > * Pekka Enberg <penberg@cs.helsinki.fi> wrote: > >>> > I think because it has zero fast path overhead and can be used > >>> > any time without enabling anything special. > > > > On Tue, Apr 28, 2009 at 12:15 PM, Ingo Molnar <mingo@elte.hu> wrote: > >> ( That's a dubious claim in any case - tracepoints are very cheap. > >> And they could be made even cheaper and such efforts would benefit > >> all the tracepoint users so it's a prime focus of interest. > >> Andi is a SystemTap proponent, right? I saw him oppose pretty much > >> everything built-in kernel tracing related. I consider that a > >> pretty extreme position. ) > > On Tue, Apr 28, 2009 at 12:19 PM, Pekka Enberg <penberg@cs.helsinki.fi> wrote: > > I have no idea how expensive tracepoints are but I suspect they don't > > make too much sense for this particular scenario. After all, kmemtrace > > is mainly interested in _allocation patterns_ whereas this patch seems > > to be more interested in "memory layout" type of things. > > That said, I do foresee a need to be able to turn on more detailed > tracing after you've identified problematic areas from kpageflags type > of overview report. And for that, you almost certainly want > kmemtrace/tracepoints style solution with pid/function/whatever regexp > matching ftrace already provides.
Exactly - kmemtrace is the tool I looked for when hunting down the page flags of the leaked ring buffer memory :-)
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