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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@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sergey Senozhatsky 2015-11-06 16:29:38 -08:00 committed by Linus Torvalds
parent 6f0b22760b
commit 6fe5186f0c
1 changed files with 13 additions and 4 deletions
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17
mm/zsmalloc.c
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@ -167,9 +167,14 @@ 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];
};
@ -448,19 +453,23 @@ 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