Hello, Minchan 2014-12-19 7:44 GMT+08:00 Minchan Kim <minchan@xxxxxxxxxx>: > Hello Ganesh, > > On Wed, Dec 17, 2014 at 03:05:19PM +0800, Ganesh Mahendran wrote: >> 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. > > It seems you are saying why debugfs_create_dir can fail but zsmalloc will not > fail by such reasons. > I don't know the internal of debugfs_create_dir but description just says > "If an error occurs, %NULL will be returned" but everyone returns ENOMEM > blindly then. Hmm, I don't think it's good but I'm okay too because it's not > our fault and others have been in there. :( > > When I look at zs_init, you don't propagate the error to user. Just missing? As the statistics collection is not essential to user, and I think we do not need to break the zsmalloc module loading when error happens in zs_stat_init()/debugfs_create_dir(). So I do not propagate the error to user and just give the message: pr_warn("zs stat initialization failed\n"); Thanks. > >> >> > >> >> + >> >> + 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/ . >> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > > -- > Kind regards, > Minchan Kim -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>