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SubjectRe: [PATCH 0/2] perf: Redesign trace events reordering
From
Date
Hi Frederic,

On Wed, 2010-05-05 at 02:03 +0200, Frederic Weisbecker wrote:
> I recently noticed that the new reordering design is broken
> when it deals with tons of events.
>
> This patchset provides another algorithm to deal with that,
> tested without any problem.
>
> And since it involves more frequent flushes, I guess it could
> plug nicely with the live mode.

Very nice! I tried these out with live mode and it seems to work fine,
after applying the patch below.

I initially had a problem with 'unexpected end of event stream' errors,
then noticed that the FINISHED_ROUND events were basically just headers
with no data, which caused the read of the 0-length payload to appear as
end-of-stream.

I'll do some more testing (and fix some warnings in the scripts that
this mode seems to elicit), but it seems so far to work pretty well for
live mode...

Tom

From: Tom Zanussi <tzanussi@gmail.com>
Date: Wed, 5 May 2010 00:27:40 -0500
Subject: [PATCH] perf/live-mode: handle payload-less events

Some events, such as the PERF_RECORD_FINISHED_ROUND event consist of
only an event header and no data. In this case, a 0-length payload
will be read, and the 0 return value will be wrongly interpreted as an
'unexpected end of event stream'.

This patch allows for proper handling of data-less events by skipping
0-length reads.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
---
tools/perf/util/session.c | 19 +++++++++++--------
1 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 9401909..00ab298 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -696,15 +696,18 @@ more:
p = &event;
p += sizeof(struct perf_event_header);

- err = do_read(self->fd, p, size - sizeof(struct perf_event_header));
- if (err <= 0) {
- if (err == 0) {
- pr_err("unexpected end of event stream\n");
- goto done;
- }
+ if (size - sizeof(struct perf_event_header)) {
+ err = do_read(self->fd, p,
+ size - sizeof(struct perf_event_header));
+ if (err <= 0) {
+ if (err == 0) {
+ pr_err("unexpected end of event stream\n");
+ goto done;
+ }

- pr_err("failed to read event data\n");
- goto out_err;
+ pr_err("failed to read event data\n");
+ goto out_err;
+ }
}

if (size == 0 ||
--
1.6.4.GIT




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