Hello, Minchan Thanks for your review. 2014-12-16 10:45 GMT+08:00 Minchan Kim <minchan@xxxxxxxxxx>: > On Sat, Dec 13, 2014 at 09:45:14PM +0800, Ganesh Mahendran wrote: >> As a ram based memory allocator, keep the fragmentation in a low level > > Just say, zsmalloc. Ok. > >> is our target. But now we still need to add the debug code in zsmalloc >> to get the quantitative data. >> >> After the RFC patch [1], Minchan Kim gave some suggestions. >> [1] https://patchwork.kernel.org/patch/5469301/ >> >> This patch adds a new configuration CONFIG_ZSMALLOC_STAT to enable the statistics >> collection for developers. Currently only the objects information in each class >> are collected. User can get the information via debugfs. For example: >> >> After I copy file 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 see the overall fragentation is: >> (37022 - 36326) / 37022 = 1.87% >> >> Also from the statistics we know why we got so low fragmentation: >> Most of the objects is in class 254 with size 4096 Bytes. The pages in >> zspage is 1. And there is only one object in a page. So, No fragmentation >> will be produced. >> >> Also we can collect other information and show it to user in the future. > > So, could you make zs Ok >> >> Signed-off-by: Ganesh Mahendran <opensource.ganesh@xxxxxxxxx> >> Suggested-by: Minchan Kim <minchan@xxxxxxxxxx> >> --- >> mm/Kconfig | 10 ++++ >> mm/zsmalloc.c | 164 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 174 insertions(+) >> >> 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 b724039..a8d0020 100644 >> --- a/mm/zsmalloc.c >> +++ b/mm/zsmalloc.c >> @@ -168,6 +168,8 @@ enum fullness_group { >> ZS_FULL >> }; >> >> +static int zs_pool_num; > > What's this? What protects the race? It is the pool index. Yes, there is problem here. I will change it to atomic and increased every time a new zs pool created. And then name the /sys/kernel/debug/pool-x using this index. static atomic_t zs_pool_index = ATOMIC_INIT(0); ... pool->index = atomic_inc_return(&zs_pool_index); > It means description. > >> + >> /* >> * number of size_classes >> */ >> @@ -200,6 +202,11 @@ struct size_class { >> /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */ >> int pages_per_zspage; >> >> +#ifdef CONFIG_ZSMALLOC_STAT >> + unsigned long obj_allocated; >> + unsigned long obj_used; >> +#endif > > I perfer creating new struct. > > struct zs_size_stat { > unsigend long obj_allocated; > unsignged long obj_used; > }; Got it, I will redo this. > >> + >> spinlock_t lock; >> >> struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS]; >> @@ -221,6 +228,10 @@ struct zs_pool { >> >> 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 +953,132 @@ static bool can_merge(struct size_class *prev, int size, int pages_per_zspage) >> return true; >> } >> >> + >> +#ifdef CONFIG_ZSMALLOC_STAT >> +#include <linux/debugfs.h> > > A question: > Why "#include" is here instead of top on the source file? Yes, the "#include ..." should be on the top of the source file. I will modify it. > >> + >> +static struct dentry *zs_stat_root; >> + >> +static int __init zs_stat_init(void) >> +{ >> + if (!debugfs_initialized()) >> + return -ENODEV; > > Do we need above check? Yes, I think we need this check. When debugfs module init failed, we should not go ahead here. > > When I read comment of debugfs_create_dir, it says > "If debugfs is not enabled in the kernel, the value -%ENODEV will be > returned." This check is not for the situation when the debugfs is not enabled. But for if we failed in debugfs_init(), then we should not use any API of debugfs. And I think "-%ENODEV will be returned" means below code in "debugfs.h" static inline struct dentry *debugfs_create_dir(const char *name, struct dentry *parent) { return ERR_PTR(-ENODEV); } > >> + >> + zs_stat_root = debugfs_create_dir("zsmalloc", NULL); >> + if (!zs_stat_root) >> + return -ENOMEM; > > On null return of debugfs_create_dir, it means always ENOMEM? Yes, you are right. -ENOMEM is not the only reason for the failure. But debugfs_create_dir does not bring back the errno. And for zsmalloc, we indeed have the permission(-EPERM) to create the entry and also we will not create duplicate(-EEXIST) entry in debufs. So, I think -ENOMEM is suitable. > >> + >> + return 0; >> +} >> + >> +static void __exit zs_stat_exit(void) >> +{ >> + debugfs_remove_recursive(zs_stat_root); >> +} >> + >> +static int zs_stats_show(struct seq_file *s, void *v) >> +{ >> + int i; >> + struct zs_pool *pool = (struct zs_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 = class->obj_allocated; >> + obj_used = class->obj_used; >> + objs_per_zspage = get_maxobj_per_zspage(class->size, >> + class->pages_per_zspage); >> + pages_used = obj_allocated / objs_per_zspage * >> + class->pages_per_zspage; > > I think We don't need to protect class->pages_per_zspage with class->lock. Yes, you are right. > >> + >> + spin_unlock(&class->lock); >> + >> + seq_printf(s, " %5u %5u %10lu %10lu %10lu\n", i, class->size, >> + obj_allocated, obj_used, pages_used); >> + >> + total_objs += class->obj_allocated; >> + total_used_objs += class->obj_used; > > You couldn't access class->fields without class lock. > Please, assign them into local variable under the lock and sum them without the lock. Got it. I will redo this. > >> + 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_open(struct inode *inode, struct file *file) >> +{ >> + return single_open(file, zs_stats_show, inode->i_private); >> +} >> + >> +static const struct file_operations zs_stats_operations = { >> + .open = zs_stats_open, >> + .read = seq_read, >> + .llseek = seq_lseek, >> + .release = single_release, >> +}; >> + >> +static int zs_pool_stat_create(struct zs_pool *pool, int index) >> +{ >> + char name[10]; >> + int ret = 0; >> + >> + if (!zs_stat_root) { >> + ret = -ENODEV; >> + goto out; >> + } >> + >> + snprintf(name, sizeof(name), "pool-%d", index); > > Hmm, how does admin know any zsmalloc instance is associated with > any block device? > Maybe we need export zspool index to the client and print it > when pool is populated. Thanks for your suggestion. > >> + pool->stat_dentry = debugfs_create_dir(name, zs_stat_root); >> + if (!pool->stat_dentry) { >> + ret = -ENOMEM; >> + goto out; >> + } >> + >> + debugfs_create_file("obj_in_classes", S_IFREG | S_IRUGO, >> + pool->stat_dentry, pool, &zs_stats_operations); > > No need to check return? It is better to check the return value and give user some information about the failure. > >> + >> +out: >> + return ret; >> +} >> + >> +static void zs_pool_stat_destroy(struct zs_pool *pool) >> +{ >> + debugfs_remove_recursive(pool->stat_dentry); >> +} >> + >> +#else /* CONFIG_ZSMALLOC_STAT */ >> + >> +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, int index) >> +{ >> + return 0; >> +} >> + >> +static inline void zs_pool_stat_destroy(struct zs_pool *pool) { } >> + >> +#endif >> + >> unsigned long zs_get_total_pages(struct zs_pool *pool) >> { >> return atomic_long_read(&pool->pages_allocated); >> @@ -1075,6 +1212,10 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size) >> atomic_long_add(class->pages_per_zspage, >> &pool->pages_allocated); >> spin_lock(&class->lock); >> +#ifdef CONFIG_ZSMALLOC_STAT >> + class->obj_allocated += get_maxobj_per_zspage(class->size, >> + class->pages_per_zspage); >> +#endif > > I prefer zs_stat_inc(class, OBJ_ALLOCATED, get_max_obj()); Got it. thanks > >> } >> >> obj = (unsigned long)first_page->freelist; >> @@ -1088,6 +1229,9 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size) >> kunmap_atomic(vaddr); >> >> first_page->inuse++; >> +#ifdef CONFIG_ZSMALLOC_STAT >> + class->obj_used++; >> +#endif > > zs_stat_inc(class, OBJ_USED, 1) OK > > >> /* Now move the zspage to another fullness group, if required */ >> fix_fullness_group(pool, first_page); >> spin_unlock(&class->lock); >> @@ -1127,12 +1271,19 @@ void zs_free(struct zs_pool *pool, unsigned long obj) >> first_page->freelist = (void *)obj; >> >> first_page->inuse--; >> +#ifdef CONFIG_ZSMALLOC_STAT >> + class->obj_used--; >> +#endif > > zs_stat_dec(class, OBJ_USED, 1) OK > >> 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); >> +#ifdef CONFIG_ZSMALLOC_STAT >> + class->obj_allocated -= get_maxobj_per_zspage(class->size, >> + class->pages_per_zspage); >> +#endif > > zs_stat_dec(class, OBJ_ALLOCATED, get_max_obj()); > >> free_zspage(first_page); >> } >> } >> @@ -1209,6 +1360,10 @@ struct zs_pool *zs_create_pool(gfp_t flags) >> } >> >> pool->flags = flags; >> + zs_pool_num++; > > Who protect the race? > And manybe we should keep the index in zspool and export it to the user > to let them know what zsmalloc instance is thiers. OK > >> + >> + if (zs_pool_stat_create(pool, zs_pool_num)) >> + pr_warn("zs pool %d stat initialization failed\n", zs_pool_num); >> >> return pool; >> >> @@ -1241,6 +1396,9 @@ void zs_destroy_pool(struct zs_pool *pool) >> kfree(class); >> } >> >> + zs_pool_stat_destroy(pool); >> + zs_pool_num--; >> + >> kfree(pool->size_class); >> kfree(pool); >> } >> @@ -1260,6 +1418,10 @@ static int __init zs_init(void) >> #ifdef CONFIG_ZPOOL >> zpool_register_driver(&zs_zpool_driver); >> #endif >> + >> + if (zs_stat_init()) >> + pr_warn("zs stat initialization failed\n"); >> + >> return 0; >> } >> >> @@ -1269,6 +1431,8 @@ static void __exit zs_exit(void) >> zpool_unregister_driver(&zs_zpool_driver); >> #endif >> zs_unregister_cpu_notifier(); >> + >> + zs_stat_exit(); >> } >> >> module_init(zs_init); >> -- >> 1.7.9.5 >> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . 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