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b=PFtmXlBeOYbR/yed4F8hkIsWHanOpThdl2FbBzxQkhc6W8viO3xMASlzIHlpuMPJO x1tY7viOOQb7Suhjpn3duHDSiZE+NwspbQ5zps3pPVrsjVotRdPaCCW2UwFnCKGHDG kaSlZ0mgbtdzuzC4zOAQaNRAKa4o5iwxjeurZO/Q= Date: Mon, 17 Mar 2025 20:43:25 -0700 From: Andrew Morton To: yangge1116@126.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, aisheng.dong@nxp.com, liuzixing@hygon.cn Subject: Re: [PATCH V2] mm/cma: using per-CMA locks to improve concurrent allocation performance Message-Id: <20250317204325.99b45373023ad2f901c1152e@linux-foundation.org> In-Reply-To: <1739152566-744-1-git-send-email-yangge1116@126.com> References: <1739152566-744-1-git-send-email-yangge1116@126.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0C6551C0003 X-Stat-Signature: bm78tk3gg4ge5husqdybgarxwoz6yj6w X-HE-Tag: 1742269406-661275 X-HE-Meta: U2FsdGVkX1/nkP4eHrrTgbH9YG6fQDYrEDtUsuh9+5IxMyMpzjdlqfE8oLNwBZhh5Ez2/p+3qE74WUA00CIKObE+lIGepiQ6YzGHhjT8zdWxmXVZxbgphj5MUmfqwQCGb+HFxcxRnEjSnzaGL9ULbzDS75pCxT9As230p/MqmpBy2GOqayNUJMd6eBx2R5MxcK000xNti7tVZrHGBLGnDygz4meNv35Y2Hl/ExzkVKyuSPUXsS+T8KBrDnAv2xQU5+OVPaa5c+iO/9wb9FzYHrwMrwObjfULpiAebTuJbw/YJ4TxCocQAx+CE4AaSBIFyHIwB46mT41gDG49m7I9sUM95jnqkdEu5zUzXZwtAwROZ7Rn8P6MpPzQDmtrPoTXvQYl3o0IPc2grcRj64OVLmSl6hw75CqrfWAb0eoK9RupwWZycwJxVafZl6S+kGEBrDpyNH4xS4q4ug5SG0ZmD0dLLsP8lq7laL3UoIk6WAF6DtqUrcu3EIf1sqaNmjhPSkyg/pfcYCtm5++NOktd7nn3KarkZwmvZvtPKy2npI8peUezYdLrDidawgtP849G5r9kt2jlZhGCBChjMWP8FEw8ijx/iQpNwjfLCzZp+HA8ebhyDjmZIWbwsG6onO2C1GxOO6YFxT74j5ej7TH0F8FgtNsu+2Pxu0qXvjAVfx4phPY2qZVqRr8W42inwAsEDvX1RM5wUs69rRjFXkOAN6H6zpY93sxuAuNRMLZPkgoPRrksD62Dnu7QCeyLwg1MYYVV9eXBQJwE/Bf9vBJN/Phrs1YyldBV256JZHjCGwRwwpxYaPSRzkpTRcwRwE0hrsnaDIBjLpS7KODD6wjV2wHPwx4Z+z4TlWdaIyvEaRrKkFHXl/Ancd+OpmbNz5Mn8otYdateN40ntkKUtHsbBDMH/L2lN3+wcQkWW+QCQO8Y6gJcO5wR4h/C3WDe0ZmQreiztdkmizLR7VB7q1d B9rfL6bj 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 10 Feb 2025 09:56:06 +0800 yangge1116@126.com wrote: > From: yangge > > 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 slove 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. This patch was in and out of mm-unstable for a while, as Frank's series "hugetlb/CMA improvements for large systems" was being added and dropped. Consequently it hasn't received any testing for a while. Below is the version which I've now re-added to mm-unstable. Can you please check this and retest it? Thanks. From: Ge Yang Subject: mm/cma: using per-CMA locks to improve concurrent allocation performance Date: Mon, 10 Feb 2025 09:56:06 +0800 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 --- mm/cma.c | 7 ++++--- mm/cma.h | 1 + 2 files changed, 5 insertions(+), 3 deletions(-) --- a/mm/cma.c~mm-cma-using-per-cma-locks-to-improve-concurrent-allocation-performance +++ a/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(str 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 *c 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; --- a/mm/cma.h~mm-cma-using-per-cma-locks-to-improve-concurrent-allocation-performance +++ a/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; _