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SubjectRe: [PATCH 2/2] mm/zsmalloc: add statistics support
On Fri, Dec 26, 2014 at 09:06:20PM +0800, Ganesh Mahendran wrote:
> Keeping fragmentation of zsmalloc in a low level is our target. But now
> we still need to add the debug code in zsmalloc to get the quantitative data.
>
> This patch adds a new configuration CONFIG_ZSMALLOC_STAT to enable the
> statistics collection for developers. Currently only the objects statatitics
> in each class are collected. User can get the information via debugfs.
> cat /sys/kernel/debug/zsmalloc/zram0/...
>
> For example:
>
> After I copied "jdk-8u25-linux-x64.tar.gz" to zram with ext4 filesystem:
> class size obj_allocated obj_used pages_used
> 0 32 0 0 0
> 1 48 256 12 3
> 2 64 64 14 1
> 3 80 51 7 1
> 4 96 128 5 3
> 5 112 73 5 2
> 6 128 32 4 1
> 7 144 0 0 0
> 8 160 0 0 0
> 9 176 0 0 0
> 10 192 0 0 0
> 11 208 0 0 0
> 12 224 0 0 0
> 13 240 0 0 0
> 14 256 16 1 1
> 15 272 15 9 1
> 16 288 0 0 0
> 17 304 0 0 0
> 18 320 0 0 0
> 19 336 0 0 0
> 20 352 0 0 0
> 21 368 0 0 0
> 22 384 0 0 0
> 23 400 0 0 0
> 24 416 0 0 0
> 25 432 0 0 0
> 26 448 0 0 0
> 27 464 0 0 0
> 28 480 0 0 0
> 29 496 33 1 4
> 30 512 0 0 0
> 31 528 0 0 0
> 32 544 0 0 0
> 33 560 0 0 0
> 34 576 0 0 0
> 35 592 0 0 0
> 36 608 0 0 0
> 37 624 0 0 0
> 38 640 0 0 0
> 40 672 0 0 0
> 42 704 0 0 0
> 43 720 17 1 3
> 44 736 0 0 0
> 46 768 0 0 0
> 49 816 0 0 0
> 51 848 0 0 0
> 52 864 14 1 3
> 54 896 0 0 0
> 57 944 13 1 3
> 58 960 0 0 0
> 62 1024 4 1 1
> 66 1088 15 2 4
> 67 1104 0 0 0
> 71 1168 0 0 0
> 74 1216 0 0 0
> 76 1248 0 0 0
> 83 1360 3 1 1
> 91 1488 11 1 4
> 94 1536 0 0 0
> 100 1632 5 1 2
> 107 1744 0 0 0
> 111 1808 9 1 4
> 126 2048 4 4 2
> 144 2336 7 3 4
> 151 2448 0 0 0
> 168 2720 15 15 10
> 190 3072 28 27 21
> 202 3264 0 0 0
> 254 4096 36209 36209 36209
>
> Total 37022 36326 36288
>
> We can calculate the overall fragentation by the last line:
> Total 37022 36326 36288
> (37022 - 36326) / 37022 = 1.87%
>
> Also by analysing objects alocated in every class we know why we got so low fragmentation:
> Most of the allocated objects is in <class 254>. And there is only 1 page in class
> 254 zspage. So, No fragmentation will be introduced by allocating objs in class 254.
>
> And in the future, we can collect other zsmalloc statistics as we need and analyse them.
>
> Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
> Suggested-by: Minchan Kim <minchan@kernel.org>
> Cc: Nitin Gupta <ngupta@vflare.org>

If you fix minors below,
Acked-by: Minchan Kim <minchan@kernel.org>

> ---
> mm/Kconfig | 10 +++
> mm/zsmalloc.c | 244 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 250 insertions(+), 4 deletions(-)
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 1d1ae6b..95c5728 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -601,6 +601,16 @@ config PGTABLE_MAPPING
> You can check speed with zsmalloc benchmark:
> https://github.com/spartacus06/zsmapbench
>
> +config ZSMALLOC_STAT
> + bool "Export zsmalloc statistics"
> + depends on ZSMALLOC
> + select DEBUG_FS
> + help
> + This option enables code in the zsmalloc to collect various
> + statistics about whats happening in zsmalloc and exports that
> + information to userspace via debugfs.
> + If unsure, say N.
> +
> config GENERIC_EARLY_IOREMAP
> bool
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 2359e61..f5ae7c6 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -91,6 +91,7 @@
> #include <linux/hardirq.h>
> #include <linux/spinlock.h>
> #include <linux/types.h>
> +#include <linux/debugfs.h>
> #include <linux/zsmalloc.h>
> #include <linux/zpool.h>
>
> @@ -168,6 +169,22 @@ enum fullness_group {
> ZS_FULL
> };
>
> +enum zs_stat_type {
> + OBJ_ALLOCATED,
> + OBJ_USED,
> +};
> +
> +#ifdef CONFIG_ZSMALLOC_STAT
> +
> +static struct dentry *zs_stat_root;
> +
> +struct zs_size_stat {
> + unsigned long obj_allocated;
> + unsigned long obj_used;
> +};

I hope you makes it array so that we could use zs_stat_type as index.
It could remove if-conditions in zs_stat_xxx.

> +
> +#endif
> +
> /*
> * number of size_classes
> */
> @@ -200,6 +217,10 @@ struct size_class {
> /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
> int pages_per_zspage;
>
> +#ifdef CONFIG_ZSMALLOC_STAT
> + struct zs_size_stat stats;
> +#endif
> +
> spinlock_t lock;
>
> struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS];
> @@ -217,10 +238,16 @@ struct link_free {
> };
>
> struct zs_pool {
> + char *name;
> +
> struct size_class **size_class;
>
> gfp_t flags; /* allocation flags used when growing pool */
> atomic_long_t pages_allocated;
> +
> +#ifdef CONFIG_ZSMALLOC_STAT
> + struct dentry *stat_dentry;
> +#endif
> };
>
> /*
> @@ -942,6 +969,177 @@ static bool can_merge(struct size_class *prev, int size, int pages_per_zspage)
> return true;
> }
>
> +#ifdef CONFIG_ZSMALLOC_STAT
> +
> +static inline void zs_stat_inc(struct size_class *class,
> + enum zs_stat_type type, unsigned long cnt)
> +{
> + if (type == OBJ_ALLOCATED)
> + class->stats.obj_allocated += cnt;
> + else if (type == OBJ_USED)
> + class->stats.obj_used += cnt;
> +}
> +
> +static inline void zs_stat_dec(struct size_class *class,
> + enum zs_stat_type type, unsigned long cnt)
> +{
> + if (type == OBJ_ALLOCATED)
> + class->stats.obj_allocated -= cnt;
> + else if (type == OBJ_USED)
> + class->stats.obj_used -= cnt;
> +}
> +
> +static inline unsigned long zs_stat_get(struct size_class *class,
> + enum zs_stat_type type)
> +{
> + if (type == OBJ_ALLOCATED)
> + return class->stats.obj_allocated;
> + else if (type == OBJ_USED)
> + return class->stats.obj_used;
> +
> + return 0;
> +}
> +
> +static int __init zs_stat_init(void)
> +{
> + if (!debugfs_initialized())
> + return -ENODEV;
> +
> + zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
> + if (!zs_stat_root)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +static void __exit zs_stat_exit(void)
> +{
> + debugfs_remove_recursive(zs_stat_root);
> +}
> +
> +static int zs_stats_size_show(struct seq_file *s, void *v)
> +{
> + int i;
> + struct zs_pool *pool = s->private;
> + struct size_class *class;
> + int objs_per_zspage;
> + unsigned long obj_allocated, obj_used, pages_used;
> + unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
> +
> + seq_printf(s, " %5s %5s %13s %10s %10s\n", "class", "size",
> + "obj_allocated", "obj_used", "pages_used");
> +
> + for (i = 0; i < zs_size_classes; i++) {
> + class = pool->size_class[i];
> +
> + if (class->index != i)
> + continue;
> +
> + spin_lock(&class->lock);
> + obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
> + obj_used = zs_stat_get(class, OBJ_USED);
> + spin_unlock(&class->lock);
> +
> + objs_per_zspage = get_maxobj_per_zspage(class->size,
> + class->pages_per_zspage);
> + pages_used = obj_allocated / objs_per_zspage *
> + class->pages_per_zspage;
> +
> + seq_printf(s, " %5u %5u %10lu %10lu %10lu\n", i,
> + class->size, obj_allocated, obj_used, pages_used);
> +
> + total_objs += obj_allocated;
> + total_used_objs += obj_used;
> + total_pages += pages_used;
> + }
> +
> + seq_puts(s, "\n");
> + seq_printf(s, " %5s %5s %10lu %10lu %10lu\n", "Total", "",
> + total_objs, total_used_objs, total_pages);
> +
> + return 0;
> +}
> +
> +static int zs_stats_size_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, zs_stats_size_show, inode->i_private);
> +}
> +
> +static const struct file_operations zs_stat_size_ops = {
> + .open = zs_stats_size_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +static int zs_pool_stat_create(char *name, struct zs_pool *pool)
> +{
> + struct dentry *entry;
> +
> + if (!zs_stat_root)
> + return -ENODEV;
> +
> + entry = debugfs_create_dir(name, zs_stat_root);
> + if (!entry) {
> + pr_warn("debugfs dir <%s> creation failed\n", name);
> + return -ENOMEM;
> + }
> + pool->stat_dentry = entry;
> +
> + entry = debugfs_create_file("obj_in_classes", S_IFREG | S_IRUGO,
> + pool->stat_dentry, pool, &zs_stat_size_ops);
> + if (!entry) {
> + pr_warn("%s: debugfs file entry <%s> creation failed\n",
> + name, "obj_in_classes");
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +static void zs_pool_stat_destroy(struct zs_pool *pool)
> +{
> + debugfs_remove_recursive(pool->stat_dentry);
> +}
> +
> +#else /* CONFIG_ZSMALLOC_STAT */
> +
> +static inline void zs_stat_inc(struct size_class *class,
> + enum zs_stat_type type, unsigned long cnt)
> +{
> +}
> +
> +static inline void zs_stat_dec(struct size_class *class,
> + enum zs_stat_type type, unsigned long cnt)
> +{
> +}
> +
> +static inline unsigned long zs_stat_get(struct size_class *class,
> + enum zs_stat_type type)
> +{
> + return 0;
> +}
> +
> +static int __init zs_stat_init(void)
> +{
> + return 0;
> +}
> +
> +static void __exit zs_stat_exit(void)
> +{
> +}
> +
> +static inline int zs_pool_stat_create(struct zs_pool *pool)

char *name, struct zs_pool *pool

Thanks for the nice work, Ganesh!

--
Kind regards,
Minchan Kim


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