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Date: Fri, 12 Dec 2014 08:40:05 +0900
From: Minchan Kim <minchan@...nel.org>
To: Ganesh Mahendran <opensource.ganesh@...il.com>
Cc: ngupta@...are.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/zsmalloc: disclose statistics to debugfs
Hello Ganesh,
On Wed, Dec 10, 2014 at 09:40:20PM +0800, Ganesh Mahendran wrote:
> As we now talk more and more about the fragmentation of zsmalloc. But
> we still need to manually add some debug code to see the fragmentation.
> So, I think we may add the statistics of memory fragmention in zsmalloc
> and disclose them to debugfs. Then we can easily get and analysis
> them when adding or developing new feature for zsmalloc.
>
> Below entries will be created when a zsmalloc pool is created:
> /sys/kernel/debug/zsmalloc/pool-n/obj_allocated
> /sys/kernel/debug/zsmalloc/pool-n/obj_used
>
> Then the status of objects usage will be:
> objects_usage = obj_used / obj_allocated
>
I didn't look at the code in detail but It would be handy for developer
but not sure we should deliver it to admin so need configurable?
How about making it per-sizeclass information, not per-pool?
So we can rely on the class->lock for the locking rule.
> Also we can collect other information and add corresponding entries
> in debugfs when needed.
>
> Signed-off-by: Ganesh Mahendran <opensource.ganesh@...il.com>
> ---
> mm/zsmalloc.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 104 insertions(+), 4 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 4d0a063..f682ef9 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -168,6 +168,8 @@ enum fullness_group {
> ZS_FULL
> };
>
> +static int zs_pool_num;
> +
> /*
> * number of size_classes
> */
> @@ -216,11 +218,19 @@ struct link_free {
> void *next;
> };
>
> +struct zs_stats {
> + atomic_long_t pages_allocated;
> + u64 obj_allocated;
> + u64 obj_used;
> +};
> +
> struct zs_pool {
> struct size_class **size_class;
>
> gfp_t flags; /* allocation flags used when growing pool */
> - atomic_long_t pages_allocated;
> +
> + struct zs_stats stats;
> + struct dentry *debugfs_dentry;
> };
>
> /*
> @@ -925,12 +935,84 @@ static void init_zs_size_classes(void)
> zs_size_classes = nr;
> }
>
> +
> +#ifdef CONFIG_DEBUG_FS
> +#include <linux/debugfs.h>
> +
> +static struct dentry *zs_debugfs_root;
> +
> +static int __init zs_debugfs_init(void)
> +{
> + if (!debugfs_initialized())
> + return -ENODEV;
> +
> + zs_debugfs_root = debugfs_create_dir("zsmalloc", NULL);
> + if (!zs_debugfs_root)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +static void __exit zs_debugfs_exit(void)
> +{
> + debugfs_remove_recursive(zs_debugfs_root);
> +}
> +
> +static int zs_pool_debugfs_create(struct zs_pool *pool, int index)
> +{
> + char name[10];
> + int ret = 0;
> +
> + if (!zs_debugfs_root) {
> + ret = -ENODEV;
> + goto out;
> + }
> +
> + snprintf(name, sizeof(name), "pool-%d", index);
> + pool->debugfs_dentry = debugfs_create_dir(name, zs_debugfs_root);
> + if (!pool->debugfs_dentry) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + debugfs_create_u64("obj_allocated", S_IRUGO, pool->debugfs_dentry,
> + &pool->stats.obj_allocated);
> + debugfs_create_u64("obj_used", S_IRUGO, pool->debugfs_dentry,
> + &pool->stats.obj_used);
> +
> +out:
> + return ret;
> +}
> +
> +static void zs_pool_debugfs_destroy(struct zs_pool *pool)
> +{
> + debugfs_remove_recursive(pool->debugfs_dentry);
> +}
> +
> +#else
> +static int __init zs_debugfs_init(void)
> +{
> + return 0;
> +}
> +
> +static void __exit zs_debugfs_exit(void) { }
> +
> +static int zs_pool_debugfs_create(struct zs_pool *pool, int index)
> +{
> + return 0;
> +}
> +
> +static void zs_pool_debugfs_destroy(struct zs_pool *pool) {}
> +#endif
> +
> static void __exit zs_exit(void)
> {
> #ifdef CONFIG_ZPOOL
> zpool_unregister_driver(&zs_zpool_driver);
> #endif
> zs_unregister_cpu_notifier();
> +
> + zs_debugfs_exit();
> }
>
> static int __init zs_init(void)
> @@ -947,6 +1029,10 @@ static int __init zs_init(void)
> #ifdef CONFIG_ZPOOL
> zpool_register_driver(&zs_zpool_driver);
> #endif
> +
> + if (zs_debugfs_init())
> + pr_warn("debugfs initialization failed\n");
> +
> return 0;
> }
>
> @@ -1039,6 +1125,11 @@ struct zs_pool *zs_create_pool(gfp_t flags)
>
> pool->flags = flags;
>
> + zs_pool_num++;
> +
> + if (zs_pool_debugfs_create(pool, zs_pool_num))
> + pr_warn("zs pool debugfs initialization failed\n");
> +
> return pool;
>
> err:
> @@ -1071,6 +1162,9 @@ void zs_destroy_pool(struct zs_pool *pool)
> }
>
> kfree(pool->size_class);
> + zs_pool_debugfs_destroy(pool);
> + zs_pool_num--;
> +
> kfree(pool);
> }
> EXPORT_SYMBOL_GPL(zs_destroy_pool);
> @@ -1110,7 +1204,9 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
>
> set_zspage_mapping(first_page, class->index, ZS_EMPTY);
> atomic_long_add(class->pages_per_zspage,
> - &pool->pages_allocated);
> + &pool->stats.pages_allocated);
> + pool->stats.obj_allocated += get_maxobj_per_zspage(class->size,
> + class->pages_per_zspage);
> spin_lock(&class->lock);
> }
>
> @@ -1125,6 +1221,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
> kunmap_atomic(vaddr);
>
> first_page->inuse++;
> + pool->stats.obj_used++;
> /* Now move the zspage to another fullness group, if required */
> fix_fullness_group(pool, first_page);
> spin_unlock(&class->lock);
> @@ -1164,12 +1261,15 @@ void zs_free(struct zs_pool *pool, unsigned long obj)
> first_page->freelist = (void *)obj;
>
> first_page->inuse--;
> + pool->stats.obj_used--;
> fullness = fix_fullness_group(pool, first_page);
> spin_unlock(&class->lock);
>
> if (fullness == ZS_EMPTY) {
> atomic_long_sub(class->pages_per_zspage,
> - &pool->pages_allocated);
> + &pool->stats.pages_allocated);
> + pool->stats.obj_allocated -= get_maxobj_per_zspage(class->size,
> + class->pages_per_zspage);
> free_zspage(first_page);
> }
> }
> @@ -1267,7 +1367,7 @@ EXPORT_SYMBOL_GPL(zs_unmap_object);
>
> unsigned long zs_get_total_pages(struct zs_pool *pool)
> {
> - return atomic_long_read(&pool->pages_allocated);
> + return atomic_long_read(&pool->stats.pages_allocated);
> }
> EXPORT_SYMBOL_GPL(zs_get_total_pages);
>
> --
> 1.7.9.5
>
> --
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--
Kind regards,
Minchan Kim
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