linux-kernel - [PATCH] oom, trace: Remove ENUM evaluation of COMPACTION

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Date:   Thu, 15 Jun 2017 06:48:23 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] oom, trace: Remove ENUM evaluation of COMPACTION_FEEDBACK

From: Steven Rostedt (VMware) <rostedt@...dmis.org>

After enabling CONFIG_TRACE_ENUM_MAP_FILE (which will soon be renamed
to CONFIG_TRACE_EVAL_MAP_FILE), I am able to examine the enums that
have been evaluated:

 # cat /sys/kernel/debug/tracing/enum_map

(which will soon be renamed to eval_map)

And it showed some interesting results:

[..]
ZONE_MOVABLE 3 (oom)
ZONE_NORMAL 2 (oom)
ZONE_DMA32 1 (oom)
ZONE_DMA 0 (oom)
3 3 (oom)
2 2 (oom)
1 1 (oom)
COMPACT_PRIO_ASYNC 2 (oom)
COMPACT_PRIO_SYNC_LIGHT 1 (oom)
COMPACT_PRIO_SYNC_FULL 0 (oom)
[..]
ZONE_DMA 0 (vmscan)
3 3 (vmscan)
2 2 (vmscan)
1 1 (vmscan)
COMPACT_PRIO_ASYNC 2 (vmscan)
[..]
ZONE_DMA 0 (kmem)
3 3 (kmem)
2 2 (kmem)
1 1 (kmem)
COMPACT_PRIO_ASYNC 2 (kmem)
[..]
ZONE_DMA 0 (compaction)
3 3 (compaction)
2 2 (compaction)
1 1 (compaction)
COMPACT_PRIO_ASYNC 2 (compaction)
[..]

The name within the parenthesis are the trace systems that the
enum/eval maps are associated with. When there's a number evaluated to
another number, that tells me that the TRACE_DEFINE_ENUM() was used on
a #define and not an enum. As #defines get converted normally, they are
not needed to be evaluated.

Each of the above trace systems with the number to number evaluation
included the file include/trace/events/mmflags.h which has:

 /* High-level compaction status feedback */
 #define COMPACTION_FAILED       1
 #define COMPACTION_WITHDRAWN    2
 #define COMPACTION_PROGRESS     3

[..]

 #define COMPACTION_FEEDBACK             \
        EM(COMPACTION_FAILED,           "failed")       \
        EM(COMPACTION_WITHDRAWN,        "withdrawn")    \
        EMe(COMPACTION_PROGRESS,        "progress")

Which is still needed for the __print_symbolic() usage in the
trace_event. But it is not needed to be evaluated.

Removing the evaluation part removes the unnecessary evaluations of
numbers to numbers.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
diff --git a/include/trace/events/mmflags.h
b/include/trace/events/mmflags.h index 304ff94..10e3663 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -257,7 +257,7 @@
IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY,	"softdirty"
)		\ COMPACTION_STATUS
 COMPACTION_PRIORITY
-COMPACTION_FEEDBACK
+/* COMPACTION_FEEDBACK are defines not enums. Not needed here. */
 ZONE_TYPE
 LRU_NAMES