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[2003:d8:2f1d:100:4f8e:bb13:c3c7:f854]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3d1052db1f0sm2828033f8f.23.2025.08.29.12.20.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 Aug 2025 12:20:15 -0700 (PDT) Message-ID: Date: Fri, 29 Aug 2025 21:20:14 +0200 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][v3] mm/hugetlb: Retry to allocate for early boot hugepage allocation To: "Li,Rongqing" , "muchun.song@linux.dev" , "osalvador@suse.de" , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "giorgitchankvetadze1997@gmail.com" References: <8c6e91ecb80c4707a52c253481cba51c@baidu.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <8c6e91ecb80c4707a52c253481cba51c@baidu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 29.08.25 17:20, Li,Rongqing wrote: > > >> On 29.08.25 11:52, lirongqing wrote: >>> From: Li RongQing >>> >>> In cloud environments with massive hugepage reservations (95%+ of >>> system RAM), single-attempt allocation during early boot often fails >>> due to memory pressure. >>> >>> Commit 91f386bf0772 ("hugetlb: batch freeing of vmemmap pages") >>> intensified this by deferring page frees, increase peak memory usage during >> allocation. >>> >>> Introduce a retry mechanism that leverages vmemmap optimization >>> reclaim (~1.6% memory) when available. Upon initial allocation >>> failure, the system retries until successful or no further progress is >>> made, ensuring reliable hugepage allocation while preserving batched >> vmemmap freeing benefits. >>> >>> Testing on a 256G machine allocating 252G of hugepages: >>> Before: 128056/129024 hugepages allocated >>> After: Successfully allocated all 129024 hugepages >>> >>> Suggested-by: David Hildenbrand >>> Signed-off-by: Li RongQing >>> --- >>> Diff with v2: auto retry mechanism >>> Diff with v1: add log if two-phase hugepage allocation is triggered >>> add the knod to control split ratio >>> >>> mm/hugetlb.c | 27 +++++++++++++++++++++++---- >>> 1 file changed, 23 insertions(+), 4 deletions(-) >>> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 753f99b..18e54ea 100644 >>> --- a/mm/hugetlb.c >>> +++ b/mm/hugetlb.c >>> @@ -3589,10 +3589,9 @@ static unsigned long __init >>> hugetlb_pages_alloc_boot(struct hstate *h) >>> >>> unsigned long jiffies_start; >>> unsigned long jiffies_end; >>> + unsigned long remaining; >>> >>> job.thread_fn = hugetlb_pages_alloc_boot_node; >>> - job.start = 0; >>> - job.size = h->max_huge_pages; >>> >>> /* >>> * job.max_threads is 25% of the available cpu threads by default. >>> @@ -3616,10 +3615,30 @@ static unsigned long __init >> hugetlb_pages_alloc_boot(struct hstate *h) >>> } >>> >>> job.max_threads = hugepage_allocation_threads; >>> - job.min_chunk = h->max_huge_pages / >> hugepage_allocation_threads; >>> >>> jiffies_start = jiffies; >>> - padata_do_multithreaded(&job); >>> + do { >>> + remaining = h->max_huge_pages - h->nr_huge_pages; >>> + >>> + job.start = h->nr_huge_pages; >>> + job.size = remaining; >>> + job.min_chunk = remaining / hugepage_allocation_threads; >>> + padata_do_multithreaded(&job); >>> + >>> + if (h->nr_huge_pages == h->max_huge_pages) >>> + break; > > If all pages are allocated, it will break out from here. Since in most cases the first allocation is successful, I have moved this check to the very beginning. Missed that, thanks! > >>> + >>> + /* >>> + * Retry allocation if vmemmap optimization is available, the >>> + * optimization frees ~1.6% of memory of hugepages, this reclaimed >>> + * memory enables additional hugepage allocations >> >> As I said, please remove any calculation details about the vmemmap. >> That's not the place to have such calculations easily become stale. >> >> Something like the following: >> >> /* >> * Retry only if the vmemmap optimization might have been able to free >> * some memory back to the system. >> */ >> > > Thanks, I will fix it > >>> + */ >>> + if (!hugetlb_vmemmap_optimizable(h)) >>> + break; >>> + >>> + /* Continue if progress was made in last iteration */ >> >> Comment wrongly indented. >> Maybe just comment above the loop that we retry as long as we are making progress instead. It's unusual to see these tail comments in loops. -- Cheers David / dhildenb