On Wed 14-12-16 18:28:38, Vlastimil Babka wrote:
> On 12/14/2016 03:53 PM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@xxxxxxxx>
> >
> > Higher order requests oom debugging is currently quite hard. We do have
> > some compaction points which can tell us how the compaction is operating
> > but there is no trace point to tell us about compaction retry logic.
> > This patch adds a one which will have the following format
> >
> > bash-3126 [001] .... 1498.220001: compact_retry: order=9 priority=COMPACT_PRIO_SYNC_LIGHT compaction_result=withdrawn retries=0 max_retries=16 should_retry=0
> >
> > we can see that the order 9 request is not retried even though we are in
> > the highest compaction priority mode becase the last compaction attempt
> > was withdrawn. This means that compaction_zonelist_suitable must have
> > returned false and there is no suitable zone to compact for this request
> > and so no need to retry further.
> >
> > another example would be
> > <...>-3137 [001] .... 81.501689: compact_retry: order=9 priority=COMPACT_PRIO_SYNC_LIGHT compaction_result=failed retries=0 max_retries=16 should_retry=0
> >
> > in this case the order-9 compaction failed to find any suitable
> > block. We do not retry anymore because this is a costly request
> > and those do not go below COMPACT_PRIO_SYNC_LIGHT priority.
> >
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> > ---
> > include/trace/events/mmflags.h | 26 ++++++++++++++++++++++++++
> > include/trace/events/oom.h | 39 +++++++++++++++++++++++++++++++++++++++
> > mm/page_alloc.c | 22 ++++++++++++++++------
> > 3 files changed, 81 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> > index 7e4cfede873c..aa4caa6914a9 100644
> > --- a/include/trace/events/mmflags.h
> > +++ b/include/trace/events/mmflags.h
> > @@ -187,8 +187,32 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
> > EM( COMPACT_NO_SUITABLE_PAGE, "no_suitable_page") \
> > EM( COMPACT_NOT_SUITABLE_ZONE, "not_suitable_zone") \
> > EMe(COMPACT_CONTENDED, "contended")
> > +
> > +/* High-level compaction status feedback */
> > +#define COMPACTION_FAILED 1
> > +#define COMPACTION_WITHDRAWN 2
> > +#define COMPACTION_PROGRESS 3
> > +
> > +#define compact_result_to_feedback(result) \
> > +({ \
> > + enum compact_result __result = result; \
> > + (compaction_failed(__result)) ? COMPACTION_FAILED : \
> > + (compaction_withdrawn(__result)) ? COMPACTION_WITHDRAWN : COMPACTION_PROGRESS; \
> > +})
>
> It seems you forgot to actually use this "function" (sorry, didn't notice
> earlier) so currently it's translating enum compact_result directly into the
> failed/withdrawn/progress strings, which is wrong.
You are right. I've screwed while integrating the enum translation part.
> The correct place for the result->feedback conversion should be
> TP_fast_assign, so __entry->result should become __entry->feedback. It's too
> late in TP_printk, as userspace tools (e.g. trace-cmd) won't know the
> functions that compact_result_to_feedback() uses.
Thanks. The follow up fix should be
---
>From 82c9064698594d694b052d3847c905e90becc7c5 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Wed, 14 Dec 2016 19:09:10 +0100
Subject: [PATCH] fold me "oom, trace: add compaction retry tracepoint"
Do not forget to translate compact_result into a highlevel constants
as per Vlastimil
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
include/trace/events/oom.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/trace/events/oom.h b/include/trace/events/oom.h
index e9d690665b7a..38baeb27221a 100644
--- a/include/trace/events/oom.h
+++ b/include/trace/events/oom.h
@@ -94,7 +94,7 @@ TRACE_EVENT(compact_retry,
TP_fast_assign(
__entry->order = order;
__entry->priority = priority;
- __entry->result = result;
+ __entry->result = compact_result_to_feedback(result);
__entry->retries = retries;
__entry->max_retries = max_retries;
__entry->ret = ret;
--
2.10.2
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>