lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 19 Sep 2014 12:48:21 +0400
From:	Alexander Yarygin <>
To:	David Ahern <>
Cc:	Arnaldo Carvalho de Melo <>,,
	Christian Borntraeger <>,
	Frederic Weisbecker <>,
	Ingo Molnar <>, Jiri Olsa <>,
	Mike Galbraith <>,
	Namhyung Kim <>,
	Paul Mackerras <>,
	Peter Zijlstra <>,
	Stephane Eranian <>,
	Alexander Yarygin <>
Subject: Re: [PATCH 1/2] perf session: Add option to copy events when queueing

David Ahern <> writes:

> On 9/18/14, 2:21 PM, David Ahern wrote:
>> On 9/18/14, 12:53 PM, Arnaldo Carvalho de Melo wrote:
>>> If nobody objects I'll merge this patch, as it fixes problems, but I
>>> wonder if the best wouldn't be simply not calling
>>> perf_evlist__mmap_consume() till the last event there is in fact
>>> consumed... I.e. as we _really_ consume the events, we remove it from
>>> there.
>>> Instead of consuming the event at perf_tool->sample() time, we would
>>> do it at perf_tool->finished_round(), would that be feasible? Has anyone
>>> tried this?
>> Hmmm... haven't tried this.  Conceptually it should work - at least
>> nothing comes to mind at the moment.
> Upon further review ...
> Alex you might want to try this first. Malloc and copy of all events
> is going to bring some serious overhead. Can avoid that if consuming
> the event in finished_round works.
> David

I've tried that:

--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -737,7 +737,6 @@ static s64 perf_kvm__mmap_read_idx(struct perf_kvm_stat *kvm, int idx,
                 * FIXME: Here we can't consume the event, as perf_session_queue_event will
                 *        point to it, and it'll get possibly overwritten by the kernel.
-               perf_evlist__mmap_consume(kvm->evlist, idx);
                if (err) {
                        pr_err("Failed to enqueue sample: %d\n", err);
@@ -787,6 +786,10 @@ static int perf_kvm__mmap_read(struct perf_kvm_stat *kvm)
        if (ntotal) {
                kvm->session->ordered_samples.next_flush = flush_time;
                err = kvm->tool.finished_round(&kvm->tool, NULL, kvm->session);
+               for (i = 0; i < kvm->evlist->nr_mmaps; i++)
+                       perf_evlist__mmap_consume(kvm->evlist, i);
                if (err) {
                        if (kvm->lost_events)
                                pr_info("\nLost events: %" PRIu64

It did't work. Turned out that there is at least one event alive after
finished_round(), usually I get more - ~20. Not sure why, maybe it's
another problem which should be solved at first?

Also, I tried to follow 'perf-top' way:

  while (perf_evlist__mmap_read() != NULL) {

I.e. without session_queue. In this case perf won't crash, but it will
process significantly less events.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists