Re: [PATCH 3/3] oom, trace: add compaction retry tracepoint
From: Vlastimil Babka
Date: Thu Dec 15 2016 - 03:18:12 EST
On 12/14/2016 07:11 PM, Michal Hocko wrote:
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bash-3126 [001] .... 1498.220001: compact_retry: order=9 priority=COMPACT_PRIO_SYNC_LIGHT compaction_result=withdrawn retries=0 max_retries=16 should_retry=0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was withdrawn.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>
OK, with that:
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
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;