From: Ge Yang Date: Mon, 10 Feb 2025 01:56:06 +0000 (+0800) Subject: mm/cma: using per-CMA locks to improve concurrent allocation performance X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=24ac6fb6e3647fff3646b3ea1811095441380560;p=users%2Fjedix%2Flinux-maple.git mm/cma: using per-CMA locks to improve concurrent allocation performance For different CMAs, concurrent allocation of CMA memory ideally should not require synchronization using locks. Currently, a global cma_mutex lock is employed to synchronize all CMA allocations, which can impact the performance of concurrent allocations across different CMAs. To test the performance impact, follow these steps: 1. Boot the kernel with the command line argument hugetlb_cma=30G to allocate a 30GB CMA area specifically for huge page allocations. (note: on my machine, which has 3 nodes, each node is initialized with 10G of CMA) 2. Use the dd command with parameters if=/dev/zero of=/dev/shm/file bs=1G count=30 to fully utilize the CMA area by writing zeroes to a file in /dev/shm. 3. Open three terminals and execute the following commands simultaneously: (Note: Each of these commands attempts to allocate 10GB [2621440 * 4KB pages] of CMA memory.) On Terminal 1: time echo 2621440 > /sys/kernel/debug/cma/hugetlb1/alloc On Terminal 2: time echo 2621440 > /sys/kernel/debug/cma/hugetlb2/alloc On Terminal 3: time echo 2621440 > /sys/kernel/debug/cma/hugetlb3/alloc We attempt to allocate pages through the CMA debug interface and use the time command to measure the duration of each allocation. Performance comparison: Without this patch With this patch Terminal1 ~7s ~7s Terminal2 ~14s ~8s Terminal3 ~21s ~7s To solve problem above, we could use per-CMA locks to improve concurrent allocation performance. This would allow each CMA to be managed independently, reducing the need for a global lock and thus improving scalability and performance. Link: https://lkml.kernel.org/r/1739152566-744-1-git-send-email-yangge1116@126.com Signed-off-by: Ge Yang Reviewed-by: Barry Song Acked-by: David Hildenbrand Reviewed-by: Oscar Salvador Cc: Aisheng Dong Cc: Baolin Wang Signed-off-by: Andrew Morton --- diff --git a/mm/cma.c b/mm/cma.c index 09322b8284bd..b06d5fe73399 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -34,7 +34,6 @@ struct cma cma_areas[MAX_CMA_AREAS]; unsigned int cma_area_count; -static DEFINE_MUTEX(cma_mutex); static int __init __cma_declare_contiguous_nid(phys_addr_t base, phys_addr_t size, phys_addr_t limit, @@ -175,6 +174,8 @@ static void __init cma_activate_area(struct cma *cma) spin_lock_init(&cma->lock); + mutex_init(&cma->alloc_mutex); + #ifdef CONFIG_CMA_DEBUGFS INIT_HLIST_HEAD(&cma->mem_head); spin_lock_init(&cma->mem_head_lock); @@ -813,9 +814,9 @@ static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr, spin_unlock_irq(&cma->lock); pfn = cmr->base_pfn + (bitmap_no << cma->order_per_bit); - mutex_lock(&cma_mutex); + mutex_lock(&cma->alloc_mutex); ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA, gfp); - mutex_unlock(&cma_mutex); + mutex_unlock(&cma->alloc_mutex); if (ret == 0) { page = pfn_to_page(pfn); break; diff --git a/mm/cma.h b/mm/cma.h index df7fc623b7a6..41a3ab0ec3de 100644 --- a/mm/cma.h +++ b/mm/cma.h @@ -39,6 +39,7 @@ struct cma { unsigned long available_count; unsigned int order_per_bit; /* Order of pages represented by one bit */ spinlock_t lock; + struct mutex alloc_mutex; #ifdef CONFIG_CMA_DEBUGFS struct hlist_head mem_head; spinlock_t mem_head_lock;