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Date: Mon, 07 Apr 2014 11:37:55 -0700
From: John Stultz <john.stultz@...aro.org>
To: KOSAKI Motohiro <kosaki.motohiro@...il.com>
CC: LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Android Kernel Team <kernel-team@...roid.com>,
Johannes Weiner <hannes@...xchg.org>,
Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>,
Hugh Dickins <hughd@...gle.com>, Dave Hansen <dave@...1.net>,
Rik van Riel <riel@...hat.com>,
Dmitry Adamushko <dmitry.adamushko@...il.com>,
Neil Brown <neilb@...e.de>,
Andrea Arcangeli <aarcange@...hat.com>,
Mike Hommey <mh@...ndium.org>, Taras Glek <tglek@...illa.com>,
Jan Kara <jack@...e.cz>, Michel Lespinasse <walken@...gle.com>,
Minchan Kim <minchan@...nel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 2/5] vrange: Add purged page detection on setting memory
non-volatile
On 03/23/2014 10:42 AM, KOSAKI Motohiro wrote:
> On Fri, Mar 21, 2014 at 2:17 PM, John Stultz <john.stultz@...aro.org> wrote:
>> Users of volatile ranges will need to know if memory was discarded.
>> This patch adds the purged state tracking required to inform userland
>> when it marks memory as non-volatile that some memory in that range
>> was purged and needs to be regenerated.
>>
>> This simplified implementation which uses some of the logic from
>> Minchan's earlier efforts, so credit to Minchan for his work.
>>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Android Kernel Team <kernel-team@...roid.com>
>> Cc: Johannes Weiner <hannes@...xchg.org>
>> Cc: Robert Love <rlove@...gle.com>
>> Cc: Mel Gorman <mel@....ul.ie>
>> Cc: Hugh Dickins <hughd@...gle.com>
>> Cc: Dave Hansen <dave@...1.net>
>> Cc: Rik van Riel <riel@...hat.com>
>> Cc: Dmitry Adamushko <dmitry.adamushko@...il.com>
>> Cc: Neil Brown <neilb@...e.de>
>> Cc: Andrea Arcangeli <aarcange@...hat.com>
>> Cc: Mike Hommey <mh@...ndium.org>
>> Cc: Taras Glek <tglek@...illa.com>
>> Cc: Jan Kara <jack@...e.cz>
>> Cc: KOSAKI Motohiro <kosaki.motohiro@...il.com>
>> Cc: Michel Lespinasse <walken@...gle.com>
>> Cc: Minchan Kim <minchan@...nel.org>
>> Cc: linux-mm@...ck.org <linux-mm@...ck.org>
>> Signed-off-by: John Stultz <john.stultz@...aro.org>
>> ---
>> include/linux/swap.h | 15 ++++++++--
>> include/linux/swapops.h | 10 +++++++
>> include/linux/vrange.h | 3 ++
>> mm/vrange.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++
>> 4 files changed, 101 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>> index 46ba0c6..18c12f9 100644
>> --- a/include/linux/swap.h
>> +++ b/include/linux/swap.h
>> @@ -70,8 +70,19 @@ static inline int current_is_kswapd(void)
>> #define SWP_HWPOISON_NUM 0
>> #endif
>>
>> -#define MAX_SWAPFILES \
>> - ((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
>> +
>> +/*
>> + * Purged volatile range pages
>> + */
>> +#define SWP_VRANGE_PURGED_NUM 1
>> +#define SWP_VRANGE_PURGED (MAX_SWAPFILES + SWP_HWPOISON_NUM + SWP_MIGRATION_NUM)
>> +
>> +
>> +#define MAX_SWAPFILES ((1 << MAX_SWAPFILES_SHIFT) \
>> + - SWP_MIGRATION_NUM \
>> + - SWP_HWPOISON_NUM \
>> + - SWP_VRANGE_PURGED_NUM \
>> + )
> This change hwpoison and migration tag number. maybe ok, maybe not.
Though depending on config can't these tag numbers change anyway?
> I'd suggest to use younger number than hwpoison.
> (That's why hwpoison uses younger number than migration)
So I can, but the way these are defined makes the results seem pretty
terrible:
#define SWP_MIGRATION_WRITE (MAX_SWAPFILES + SWP_HWPOISON_NUM \
+ SWP_MVOLATILE_PURGED_NUM + 1)
Particularly when:
#define MAX_SWAPFILES ((1 << MAX_SWAPFILES_SHIFT) \
- SWP_MIGRATION_NUM \
- SWP_HWPOISON_NUM \
- SWP_MVOLATILE_PURGED_NUM \
)
Its a lot of unnecessary mental gymnastics. Yuck.
Would a general cleanup like the following be ok to try to make this
more extensible?
thanks
-john
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 3507115..21387df 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -49,29 +49,38 @@ static inline int current_is_kswapd(void)
* actions on faults.
*/
+enum {
+ /*
+ * NOTE: We use the high bits here (subtracting from
+ * 1<<MAX_SWPFILES_SHIFT), so to preserve the values insert
+ * new entries here at the top of the enum, not at the bottom
+ */
+#ifdef CONFIG_MEMORY_FAILURE
+ SWP_HWPOISON_NR,
+#endif
+#ifdef CONFIG_MIGRATION
+ SWP_MIGRATION_READ_NR,
+ SWP_MIGRATION_WRITE_NR,
+#endif
+ SWP_MAX_NR,
+};
+#define MAX_SWAPFILES ((1 << MAX_SWAPFILES_SHIFT) - SWP_MAX_NR)
+
/*
* NUMA node memory migration support
*/
#ifdef CONFIG_MIGRATION
-#define SWP_MIGRATION_NUM 2
-#define SWP_MIGRATION_READ (MAX_SWAPFILES + SWP_HWPOISON_NUM)
-#define SWP_MIGRATION_WRITE (MAX_SWAPFILES + SWP_HWPOISON_NUM + 1)
-#else
-#define SWP_MIGRATION_NUM 0
+#define SWP_MIGRATION_READ (MAX_SWAPFILES + SWP_MIGRATION_READ_NR)
+#define SWP_MIGRATION_WRITE (MAX_SWAPFILES + SWP_MIGRATION_WRITE_NR)
#endif
/*
* Handling of hardware poisoned pages with memory corruption.
*/
#ifdef CONFIG_MEMORY_FAILURE
-#define SWP_HWPOISON_NUM 1
-#define SWP_HWPOISON MAX_SWAPFILES
-#else
-#define SWP_HWPOISON_NUM 0
+#define SWP_HWPOISON (MAX_SWAPFILES + SWP_HWPOISON_NR)
#endif
-#define MAX_SWAPFILES \
- ((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
/*
* Magic header for a swap area. The first part of the union is
--
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