Commit 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records") has an
unintended side-effect of also suppressing all AUX records with no flags
and non-zero size, so all the regular records in the full trace mode.
This breaks some use cases for people.
Fix this by restoring "regular" AUX records.
Signed-off-by: Alexander Shishkin <[email protected]>
Fixes: 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records")
Reported-by: Ben Gainey <[email protected]>
Tested-by: Ben Gainey <[email protected]>
CC: [email protected] # v4.20+
---
kernel/events/ring_buffer.c | 33 +++++++++++++++------------------
1 file changed, 15 insertions(+), 18 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 678ccec60d8f..626256dc26c1 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -455,24 +455,21 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
rb->aux_head += size;
}
- if (size || handle->aux_flags) {
- /*
- * Only send RECORD_AUX if we have something useful to communicate
- *
- * Note: the OVERWRITE records by themselves are not considered
- * useful, as they don't communicate any *new* information,
- * aside from the short-lived offset, that becomes history at
- * the next event sched-in and therefore isn't useful.
- * The userspace that needs to copy out AUX data in overwrite
- * mode should know to use user_page::aux_head for the actual
- * offset. So, from now on we don't output AUX records that
- * have *only* OVERWRITE flag set.
- */
-
- if (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE)
- perf_event_aux_event(handle->event, aux_head, size,
- handle->aux_flags);
- }
+ /*
+ * Only send RECORD_AUX if we have something useful to communicate
+ *
+ * Note: the OVERWRITE records by themselves are not considered
+ * useful, as they don't communicate any *new* information,
+ * aside from the short-lived offset, that becomes history at
+ * the next event sched-in and therefore isn't useful.
+ * The userspace that needs to copy out AUX data in overwrite
+ * mode should know to use user_page::aux_head for the actual
+ * offset. So, from now on we don't output AUX records that
+ * have *only* OVERWRITE flag set.
+ */
+ if (size || (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE))
+ perf_event_aux_event(handle->event, aux_head, size,
+ handle->aux_flags);
rb->user_page->aux_head = rb->aux_head;
if (rb_need_aux_wakeup(rb))
--
2.20.1
Hi Alex
I was just wondering if this was expected to make 5.1? (I could not see
it in RC5)?
Thanks
Ben
On Fri, 2019-03-29 at 11:13 +0200, Alexander Shishkin wrote:
> Commit 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records") has
> an
> unintended side-effect of also suppressing all AUX records with no
> flags
> and non-zero size, so all the regular records in the full trace mode.
> This breaks some use cases for people.
>
> Fix this by restoring "regular" AUX records.
>
> Signed-off-by: Alexander Shishkin <[email protected]
> >
> Fixes: 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records")
> Reported-by: Ben Gainey <[email protected]>
> Tested-by: Ben Gainey <[email protected]>
> CC: [email protected] # v4.20+
> ---
> kernel/events/ring_buffer.c | 33 +++++++++++++++------------------
> 1 file changed, 15 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/events/ring_buffer.c
> b/kernel/events/ring_buffer.c
> index 678ccec60d8f..626256dc26c1 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -455,24 +455,21 @@ void perf_aux_output_end(struct
> perf_output_handle *handle, unsigned long size)
> rb->aux_head += size;
> }
>
> -if (size || handle->aux_flags) {
> -/*
> - * Only send RECORD_AUX if we have something useful to
> communicate
> - *
> - * Note: the OVERWRITE records by themselves are not
> considered
> - * useful, as they don't communicate any *new*
> information,
> - * aside from the short-lived offset, that becomes
> history at
> - * the next event sched-in and therefore isn't useful.
> - * The userspace that needs to copy out AUX data in
> overwrite
> - * mode should know to use user_page::aux_head for the
> actual
> - * offset. So, from now on we don't output AUX records
> that
> - * have *only* OVERWRITE flag set.
> - */
> -
> -if (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE)
> -perf_event_aux_event(handle->event, aux_head,
> size,
> - handle->aux_flags);
> -}
> +/*
> + * Only send RECORD_AUX if we have something useful to
> communicate
> + *
> + * Note: the OVERWRITE records by themselves are not considered
> + * useful, as they don't communicate any *new* information,
> + * aside from the short-lived offset, that becomes history at
> + * the next event sched-in and therefore isn't useful.
> + * The userspace that needs to copy out AUX data in overwrite
> + * mode should know to use user_page::aux_head for the actual
> + * offset. So, from now on we don't output AUX records that
> + * have *only* OVERWRITE flag set.
> + */
> +if (size || (handle->aux_flags &
> ~(u64)PERF_AUX_FLAG_OVERWRITE))
> +perf_event_aux_event(handle->event, aux_head, size,
> + handle->aux_flags);
>
> rb->user_page->aux_head = rb->aux_head;
> if (rb_need_aux_wakeup(rb))
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On Mon, Apr 15, 2019 at 08:04:33AM +0000, Ben Gainey wrote:
> Hi Alex
>
> I was just wondering if this was expected to make 5.1? (I could not see
> it in RC5)?
Yikes, I forgot about this again, didn't I ?
At least, they appear to still apply, so I've queued them. Not sure
they'll still make this release, but at least they should not go missing
_again_.
Thanks Peter :-)
On Mon, 2019-04-15 at 11:16 +0200, Peter Zijlstra wrote:
> On Mon, Apr 15, 2019 at 08:04:33AM +0000, Ben Gainey wrote:
> > Hi Alex
> >
> > I was just wondering if this was expected to make 5.1? (I could not
> > see
> > it in RC5)?
>
> Yikes, I forgot about this again, didn't I ?
>
> At least, they appear to still apply, so I've queued them. Not sure
> they'll still make this release, but at least they should not go
> missing
> _again_.
Commit-ID: 339bc4183596e1f68c2c98a03b87aa124107c317
Gitweb: https://git.kernel.org/tip/339bc4183596e1f68c2c98a03b87aa124107c317
Author: Alexander Shishkin <[email protected]>
AuthorDate: Fri, 29 Mar 2019 11:13:38 +0200
Committer: Ingo Molnar <[email protected]>
CommitDate: Tue, 16 Apr 2019 12:13:57 +0200
perf/ring_buffer: Fix AUX record suppression
The following commit:
1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records")
has an unintended side-effect of also suppressing all AUX records with no flags
and non-zero size, so all the regular records in the full trace mode.
This breaks some use cases for people.
Fix this by restoring "regular" AUX records.
Reported-by: Ben Gainey <[email protected]>
Tested-by: Ben Gainey <[email protected]>
Signed-off-by: Alexander Shishkin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Fixes: 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records")
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/events/ring_buffer.c | 33 +++++++++++++++------------------
1 file changed, 15 insertions(+), 18 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 2545ac08cc77..5eedb49a65ea 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -455,24 +455,21 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
rb->aux_head += size;
}
- if (size || handle->aux_flags) {
- /*
- * Only send RECORD_AUX if we have something useful to communicate
- *
- * Note: the OVERWRITE records by themselves are not considered
- * useful, as they don't communicate any *new* information,
- * aside from the short-lived offset, that becomes history at
- * the next event sched-in and therefore isn't useful.
- * The userspace that needs to copy out AUX data in overwrite
- * mode should know to use user_page::aux_head for the actual
- * offset. So, from now on we don't output AUX records that
- * have *only* OVERWRITE flag set.
- */
-
- if (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE)
- perf_event_aux_event(handle->event, aux_head, size,
- handle->aux_flags);
- }
+ /*
+ * Only send RECORD_AUX if we have something useful to communicate
+ *
+ * Note: the OVERWRITE records by themselves are not considered
+ * useful, as they don't communicate any *new* information,
+ * aside from the short-lived offset, that becomes history at
+ * the next event sched-in and therefore isn't useful.
+ * The userspace that needs to copy out AUX data in overwrite
+ * mode should know to use user_page::aux_head for the actual
+ * offset. So, from now on we don't output AUX records that
+ * have *only* OVERWRITE flag set.
+ */
+ if (size || (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE))
+ perf_event_aux_event(handle->event, aux_head, size,
+ handle->aux_flags);
rb->user_page->aux_head = rb->aux_head;
if (rb_need_aux_wakeup(rb))