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Message-Id: <1444968090-7066-1-git-send-email-sergey.senozhatsky@gmail.com>
Date: Fri, 16 Oct 2015 13:01:30 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To: Minchan Kim <minchan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH] zsmalloc: reduce size_class memory usage
Each `struct size_class' contains `struct zs_size_stat':
an array of NR_ZS_STAT_TYPE `unsigned long'. For zsmalloc
built with no CONFIG_ZSMALLOC_STAT this results in a waste
of `2 * sizeof(unsigned long)' per-class.
The patch removes unneeded `struct zs_size_stat' members
by redefining NR_ZS_STAT_TYPE (max stat idx in array).
Since both NR_ZS_STAT_TYPE and zs_stat_type are compile time
constants, GCC can eliminate zs_stat_inc()/zs_stat_dec() calls
that use zs_stat_type larger than NR_ZS_STAT_TYPE:
CLASS_ALMOST_EMPTY and CLASS_ALMOST_FULL at the moment.
./scripts/bloat-o-meter mm/zsmalloc.o.old mm/zsmalloc.o.new
add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-39 (-39)
function old new delta
fix_fullness_group 97 94 -3
insert_zspage 100 86 -14
remove_zspage 141 119 -22
To summarize:
a) each class now uses less memory
b) we avoid a number of dec/inc stats (a minor optimization,
but still).
The gain will increase once we introduce additional stats.
A simple IO test.
iozone -t 4 -R -r 32K -s 60M -I +Z
patched base
" Initial write " 4145599.06 4127509.75
" Rewrite " 4146225.94 4223618.50
" Read " 17157606.00 17211329.50
" Re-read " 17380428.00 17267650.50
" Reverse Read " 16742768.00 16162732.75
" Stride read " 16586245.75 16073934.25
" Random read " 16349587.50 15799401.75
" Mixed workload " 10344230.62 9775551.50
" Random write " 4277700.62 4260019.69
" Pwrite " 4302049.12 4313703.88
" Pread " 6164463.16 6126536.72
" Fwrite " 7131195.00 6952586.00
" Fread " 12682602.25 12619207.50
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
mm/zsmalloc.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 2500ee8..0331c9a9 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -166,9 +166,14 @@ enum zs_stat_type {
OBJ_USED,
CLASS_ALMOST_FULL,
CLASS_ALMOST_EMPTY,
- NR_ZS_STAT_TYPE,
};
+#ifdef CONFIG_ZSMALLOC_STAT
+#define NR_ZS_STAT_TYPE (CLASS_ALMOST_EMPTY + 1)
+#else
+#define NR_ZS_STAT_TYPE (OBJ_USED + 1)
+#endif
+
struct zs_size_stat {
unsigned long objs[NR_ZS_STAT_TYPE];
};
@@ -447,19 +452,23 @@ static int get_size_class_index(int size)
static inline void zs_stat_inc(struct size_class *class,
enum zs_stat_type type, unsigned long cnt)
{
- class->stats.objs[type] += cnt;
+ if (type < NR_ZS_STAT_TYPE)
+ class->stats.objs[type] += cnt;
}
static inline void zs_stat_dec(struct size_class *class,
enum zs_stat_type type, unsigned long cnt)
{
- class->stats.objs[type] -= cnt;
+ if (type < NR_ZS_STAT_TYPE)
+ class->stats.objs[type] -= cnt;
}
static inline unsigned long zs_stat_get(struct size_class *class,
enum zs_stat_type type)
{
- return class->stats.objs[type];
+ if (type < NR_ZS_STAT_TYPE)
+ return class->stats.objs[type];
+ return 0;
}
#ifdef CONFIG_ZSMALLOC_STAT
--
2.6.1.134.g4b1fd35
--
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