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Message-ID: <CAAmzW4MkS5M+X+e9w=zv873jjfMxqQxtpNTz3EAkxa+f5WnK4A@mail.gmail.com>
Date: Tue, 24 Mar 2015 14:26:39 +0900
From: Joonsoo Kim <js1304@...il.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Jiri Olsa <jolsa@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
David Ahern <dsahern@...il.com>,
Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH 2/5] perf kmem: Analyze page allocator events also
2015-03-24 9:18 GMT+09:00 Namhyung Kim <namhyung@...nel.org>:
> On Tue, Mar 24, 2015 at 02:32:17AM +0900, Joonsoo Kim wrote:
>> 2015-03-23 15:30 GMT+09:00 Namhyung Kim <namhyung@...nel.org>:
>> > The perf kmem command records and analyze kernel memory allocation
>> > only for SLAB objects. This patch implement a simple page allocator
>> > analyzer using kmem:mm_page_alloc and kmem:mm_page_free events.
>> >
>> > It adds two new options of --slab and --page. The --slab option is
>> > for analyzing SLAB allocator and that's what perf kmem currently does.
>> >
>> > The new --page option enables page allocator events and analyze kernel
>> > memory usage in page unit. Currently, 'stat --alloc' subcommand is
>> > implemented only.
>> >
>> > If none of these --slab nor --page is specified, --slab is implied.
>> >
>> > # perf kmem stat --page --alloc --line 10
>> >
>> > -------------------------------------------------------------------------------------
>> > Page | Total alloc (KB) | Hits | Order | Migration type | GFP flags
>> > -------------------------------------------------------------------------------------
>> > ffffea0015e48e00 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea0015e47400 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea001440f600 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea001440cc00 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea00140c6300 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea00140c5c00 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea00140c5000 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea00140c4f00 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea00140c4e00 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ffffea00140c4d00 | 16 | 1 | 2 | RECLAIMABLE | 00285250
>> > ... | ... | ... | ... | ... | ...
>> > -------------------------------------------------------------------------------------
>>
>> Tracepoint on mm_page_alloc print out pfn as well as pointer of struct page.
>> How about printing pfn rather than pointer of struct page?
>
> I'd really like to have pfn rather than struct page. But I don't know
> how to convert page pointer to pfn in userspace.
>
> The output of tracepoint via $debugfs/tracing/trace file is generated
> from kernel-side, so it can easily have pfn from page pointer. But
> tracepoint itself only saves page pointer and we need to convert/print
> it in userspace.
Ah...I didn't realize that perf don't use output of $debugfs/tracing/trace
file. So, perf just uses raw trace buffer directly? If pfn is saved to
the trace buffer, perf can print pfn rather than pointer of struct page?
> Yes, perf script (or libtraceevent) shows pfn when printing those
> events. But that's bogus since it cannot determine the size of the
> struct page so the pointer arithmetic in open-coded page_to_pfn()
> which is saved in the print_fmt of the tracepoint will end up with an
> normal integer arithmatic.
How about following change and making 'perf kmem' print pfn?
If we store pfn on the trace buffer, we can print $debugfs/tracing/trace
as is and 'perf kmem' can also print pfn.
Thanks.
diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 4ad10ba..9dcfd0b 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -199,22 +199,22 @@ TRACE_EVENT(mm_page_alloc,
TP_ARGS(page, order, gfp_flags, migratetype),
TP_STRUCT__entry(
- __field( struct page *, page )
+ __field( unsigned long, pfn )
__field( unsigned int, order )
__field( gfp_t, gfp_flags )
__field( int, migratetype )
),
TP_fast_assign(
- __entry->page = page;
+ __entry->pfn = page ? page_to_pfn(page) : -1;
__entry->order = order;
__entry->gfp_flags = gfp_flags;
__entry->migratetype = migratetype;
),
TP_printk("page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s",
- __entry->page,
- __entry->page ? page_to_pfn(__entry->page) : 0,
+ __entry->pfn != -1 ? pfn_to_page(__entry->pfn) : NULL,
+ __entry->pfn != -1 ? __entry->pfn : 0,
__entry->order,
__entry->migratetype,
show_gfp_flags(__entry->gfp_flags))
--
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