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[2003:cb:c734:b800:12c4:65cd:348a:aee6]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38dc565d62dsm10391540f8f.93.2025.02.10.00.34.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Feb 2025 00:34:47 -0800 (PST) Message-ID: <51514ffd-a1ca-4eb4-90ab-c6871ab92c95@redhat.com> Date: Mon, 10 Feb 2025 09:34:46 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm/cma: using per-CMA locks to improve concurrent allocation performance To: yangge1116@126.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 21cnbao@gmail.com, baolin.wang@linux.alibaba.com, aisheng.dong@nxp.com, liuzixing@hygon.cn References: <1739152566-744-1-git-send-email-yangge1116@126.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <1739152566-744-1-git-send-email-yangge1116@126.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10.02.25 02:56, 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 > Hi, I'm curious, what is the real workload you are trying to optimize for? I assume this example here is just to have some measurement. Is concurrency within a single CMA area also a problem for your use case? > 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. > > Signed-off-by: yangge > --- > > V2: > - update code and message suggested by Barry. > > mm/cma.c | 7 ++++--- > mm/cma.h | 1 + > 2 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/mm/cma.c b/mm/cma.c > index 34a4df2..a0d4d2f 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); As raised, a better approach might be to return -EAGAIN in case we hit an isolated pageblock and deal with that more gracefully here (e.g., try another block, or retry this one if there are not others left, ...) In any case, this change here looks like an improvement. Acked-by: David Hildenbrand -- Cheers, David / dhildenb