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SubjectRe: [PATCH 2/6] tracing, page-allocator: Add trace events for anti-fragmentation falling back to other migratetypes

* Mel Gorman <mel@csn.ul.ie> wrote:

> On Fri, Aug 07, 2009 at 10:02:49AM +0200, Ingo Molnar wrote:
> >
> > * Mel Gorman <mel@csn.ul.ie> wrote:
> >
> > > +++ b/mm/page_alloc.c
> > > @@ -839,6 +839,12 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
> > > start_migratetype);
> > >
> > > expand(zone, page, order, current_order, area, migratetype);
> > > +
> > > + trace_mm_page_alloc_extfrag(page, order, current_order,
> > > + start_migratetype, migratetype,
> > > + current_order < pageblock_order,
> > > + migratetype == start_migratetype);
> >
> > This tracepoint too should be optimized some more:
> >
> > - pageblock_order can be passed down verbatim instead of the
> > 'current_order < pageblock_order': it means one comparison less
> > in the fast-path, plus it gives more trace information as well.
> >
> > - migratetype == start_migratetype check is superfluous as both
> > values are already traced. This property can be added to the
> > TP_printk() post-processing stage instead, if the pretty-printing
> > is desired.
> >
>
> I think what you're saying that it's better to handle additional
> information like this in TP_printk always. That's what I've
> changed both of these into at least. I didn't even need to pass
> down pageblock_order because it should be available in the
> post-processing context from a header.

yeah. I formulated my suggestions in a trace-output-invariant way.
If some information can be omitted altogether from the trace, the
better.

> The additional parameters are not being passed down any more and
> the TP_printk looks like
>
> TP_printk("page=%p pfn=%lu alloc_order=%d fallback_order=%d pageblock_order=%d alloc_migratetype=%d fallback_migratetype=%d fragmenting=%d change_ownership=%d",
> __entry->page,
> page_to_pfn(__entry->page),
> __entry->alloc_order,
> __entry->fallback_order,
> pageblock_order,
> __entry->alloc_migratetype,
> __entry->fallback_migratetype,
> __entry->fallback_order < pageblock_order,
> __entry->alloc_migratetype == __entry->fallback_migratetype)
>
> Is that what you meant?

yeah, this looks more compact.

A detail: we might still want to pass in pageblock_order somehow -
for example 'perf' will get access to the raw binary record but wont
run the above printk line.

Ingo


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