Re: [PATCH 4/4] perf kvm: fix bug resolving guest kernel syms
From: David Ahern
Date: Tue Jul 10 2012 - 22:23:13 EST
On 7/10/12 6:54 PM, Namhyung Kim wrote:
Hi, David
On Tue, 10 Jul 2012 15:48:14 -0600, David Ahern wrote:
Guest kernel symbols are not resolved despite passing the information
needed to resolve them. e.g.,
perf kvm --guest --guestmount=/tmp/guest-mount record -a -- sleep 1
perf kvm --guest --guestmount=/tmp/guest-mount report --stdio
36.55% [guest/11399] [unknown] [g] 0xffffffff81600bc8
33.19% [guest/10474] [unknown] [g] 0x00000000c0116e00
30.26% [guest/11094] [unknown] [g] 0xffffffff8100a288
43.69% [guest/10474] [unknown] [g] 0x00000000c0103d90
37.38% [guest/11399] [unknown] [g] 0xffffffff81600bc8
12.24% [guest/11094] [unknown] [g] 0xffffffff810aa91d
6.69% [guest/11094] [unknown] [u] 0x00007fa784d721c3
which is just pathetic.
After a maddening 2 days sifting through perf minutia I found it --
id_hdr_size is not initialized for guest machines. This shows up on the
report side as random garbage for the cpu and timestamp, e.g.,
29816 7310572949125804849 0x1ac0 [0x50]: PERF_RECORD_MMAP ...
that messes up the sample sorting such that synthesized guest maps are
processed last.
With this patch you get a much more helpful report:
12.11% [guest/11399] [guest.kernel.kallsyms.11399] [g] irqtime_account_process_tick
10.58% [guest/11399] [guest.kernel.kallsyms.11399] [g] run_timer_softirq
6.95% [guest/11094] [guest.kernel.kallsyms.11094] [g] printk_needs_cpu
6.50% [guest/11094] [guest.kernel.kallsyms.11094] [g] do_timer
6.45% [guest/11399] [guest.kernel.kallsyms.11399] [g] idle_balance
4.90% [guest/11094] [guest.kernel.kallsyms.11094] [g] native_read_tsc
...
Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
tools/perf/util/map.c | 24 ++++++++++++++++++++++++
tools/perf/util/map.h | 1 +
tools/perf/util/session.c | 1 +
3 files changed, 26 insertions(+)
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 641377e..da3411b 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -730,3 +730,27 @@ char *machine__mmap_name(struct machine *self, char *bf, size_t size)
return bf;
}
+
+void machines__set_id_hdr_size(struct rb_root *self, u16 id_hdr_size)
+{
+ struct rb_node *p;
+ struct machine *machine;
+
+ p = self->rb_node;
+ while (p != NULL) {
+ machine = rb_entry(p, struct machine, rb_node);
+ machine->id_hdr_size = id_hdr_size;
+ p = rb_next(p);
+ }
+
Looks like white-space damaged. :(
bleah, something on my dev server converted tabs to spaces. Will fix.
The loop itself looks fine, or you might use this form:
for (p = rb_first(self); p; p = rb_next(p))
Doesn't work - I still see machines not updated.
Is there a something like rb_for_each_entry() ?
Didn't see one.
+ p = self->rb_node;
+ if (p)
+ p = rb_prev(p);
+ while (p != NULL) {
+ machine = rb_entry(p, struct machine, rb_node);
+ machine->id_hdr_size = id_hdr_size;
+ p = rb_prev(p);
+ }
+
I don't see why this second loop is necessary?
To get the left half of the tree I believe. First loop walks the root
and all of the leaves to the right; this loop walks all of the leaves to
the left.
David
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