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>
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index a8ff24a..2858b20 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -167,9 +167,14 @@
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 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