linux-kernel - Re: [PATCH] mm/debug: sync up latest migrate_reason to migrate_reason

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Date:   Sat, 18 Sep 2021 22:38:10 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Weizhao Ouyang <o451686892@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Oscar Salvador <osalvador@...e.de>,
        Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/debug: sync up latest migrate_reason to
 migrate_reason_names

On 9/18/21 00:03, Weizhao Ouyang wrote:
...
>   
> Anyway, I didn't find a simply way the build the "everywhere" relationship behind
> the packaged TRACE_DEFINE_ENUM , what do you think.
> 
It's actually pretty easy, unless I'm unknowingly violating some rule
here. But I did review tracing a bit before diving in, and I think this
is reasonable.

The trace macros EM(), EMe(), and MIGRATE_REASON are flexible enough to
get whatever you want, out of them. So, the trace header can be the one
location for the definition of the enum-to-string mapping.

The key is to move the enum to a common header file that both the trace
system (trace/events/migrate.h) and the migrate header
(include/linux/migrate.h) can include. Fortunately, that's already been
started for enum migrate_mode: there is migrate_mode.h.

So it all works approximately like this, below. (I'll attach a
white-space-correct diff that you can apply directly, too). I've
compiled tested and rebooted with it, but haven't checked much more
than that yet.

---
  include/linux/migrate.h      | 16 ++--------------
  include/linux/migrate_mode.h | 13 +++++++++++++
  mm/debug.c                   | 19 ++++++++++++-------
  3 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 326250996b4e..cb62fbc3d8d6 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -6,6 +6,7 @@
  #include <linux/mempolicy.h>
  #include <linux/migrate_mode.h>
  #include <linux/hugetlb.h>
+#include <linux/migrate_mode.h>

  typedef struct page *new_page_t(struct page *page, unsigned long private);
  typedef void free_page_t(struct page *page, unsigned long private);
@@ -19,20 +20,7 @@ struct migration_target_control;
   */
  #define MIGRATEPAGE_SUCCESS		0

-enum migrate_reason {
-	MR_COMPACTION,
-	MR_MEMORY_FAILURE,
-	MR_MEMORY_HOTPLUG,
-	MR_SYSCALL,		/* also applies to cpusets */
-	MR_MEMPOLICY_MBIND,
-	MR_NUMA_MISPLACED,
-	MR_CONTIG_RANGE,
-	MR_LONGTERM_PIN,
-	MR_DEMOTION,
-	MR_TYPES
-};
-
-/* In mm/debug.c; also keep sync with include/trace/events/migrate.h */
+/* In mm/debug.c */
  extern const char *migrate_reason_names[MR_TYPES];

  #ifdef CONFIG_MIGRATION
diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
index 883c99249033..f37cc03f9369 100644
--- a/include/linux/migrate_mode.h
+++ b/include/linux/migrate_mode.h
@@ -19,4 +19,17 @@ enum migrate_mode {
  	MIGRATE_SYNC_NO_COPY,
  };

+enum migrate_reason {
+	MR_COMPACTION,
+	MR_MEMORY_FAILURE,
+	MR_MEMORY_HOTPLUG,
+	MR_SYSCALL,		/* also applies to cpusets */
+	MR_MEMPOLICY_MBIND,
+	MR_NUMA_MISPLACED,
+	MR_CONTIG_RANGE,
+	MR_LONGTERM_PIN,
+	MR_DEMOTION,
+	MR_TYPES
+};
+
  #endif		/* MIGRATE_MODE_H_INCLUDED */
diff --git a/mm/debug.c b/mm/debug.c
index e73fe0a8ec3d..51152ffc1f29 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -17,14 +17,19 @@

  #include "internal.h"

+#include <trace/events/migrate.h>
+
+/*
+ * Define EM() and EMe() so that MIGRATE_REASON from trace/events/migrate.h can
+ * be used to populate migrate_reason_names[].
+ */
+#undef EM
+#undef EMe
+#define EM(a, b)	b,
+#define EMe(a, b)	b
+
  const char *migrate_reason_names[MR_TYPES] = {
-	"compaction",
-	"memory_failure",
-	"memory_hotplug",
-	"syscall_or_cpuset",
-	"mempolicy_mbind",
-	"numa_misplaced",
-	"cma",
+	MIGRATE_REASON
  };

  const struct trace_print_flags pageflag_names[] = {
-- 
2.33.0

thanks,
-- 
John Hubbard
NVIDIA
View attachment "0001-Use-one-definition-of-MIGRATE_REASON-strings-everywh.patch" of type "text/x-patch" (2704 bytes)