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| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2014-01-21 15:49:07 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-21 16:19:44 -0800 |
| commit | b35f1819acd9243a3ff7ad25b1fa8bd6bfe80fb2 (patch) | |
| tree | 140f810d09226caa12531e0a02126af64e71e314 /mm/memory.c | |
| parent | 943dca1a1fcbccb58de944669b833fd38a6c809b (diff) | |
| download | op-kernel-dev-b35f1819acd9243a3ff7ad25b1fa8bd6bfe80fb2.zip op-kernel-dev-b35f1819acd9243a3ff7ad25b1fa8bd6bfe80fb2.tar.gz | |
mm: create a separate slab for page->ptl allocation
If DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC are enabled spinlock_t on x86_64
is 72 bytes. For page->ptl they will be allocated from kmalloc-96 slab,
so we loose 24 on each. An average system can easily allocate few tens
thousands of page->ptl and overhead is significant.
Let's create a separate slab for page->ptl allocation to solve this.
To make sure that it really works this time, some numbers from my test
machine (just booted, no load):
Before:
# grep '^\(kmalloc-96\|page->ptl\)' /proc/slabinfo
kmalloc-96 31987 32190 128 30 1 : tunables 120 60 8 : slabdata 1073 1073 92
After:
# grep '^\(kmalloc-96\|page->ptl\)' /proc/slabinfo
page->ptl 27516 28143 72 53 1 : tunables 120 60 8 : slabdata 531 531 9
kmalloc-96 3853 5280 128 30 1 : tunables 120 60 8 : slabdata 176 176 0
Note that the patch is useful not only for debug case, but also for
PREEMPT_RT, where spinlock_t is always bloated.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/mm/memory.c b/mm/memory.c index e9c5504..86487df 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4275,11 +4275,20 @@ void copy_user_huge_page(struct page *dst, struct page *src, #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */ #if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS + +static struct kmem_cache *page_ptl_cachep; + +void __init ptlock_cache_init(void) +{ + page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0, + SLAB_PANIC, NULL); +} + bool ptlock_alloc(struct page *page) { spinlock_t *ptl; - ptl = kmalloc(sizeof(spinlock_t), GFP_KERNEL); + ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL); if (!ptl) return false; page->ptl = ptl; @@ -4288,6 +4297,6 @@ bool ptlock_alloc(struct page *page) void ptlock_free(struct page *page) { - kfree(page->ptl); + kmem_cache_free(page_ptl_cachep, page->ptl); } #endif |
