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Thu, 05 Jun 2025 08:44:10 +0800 (CST) Message-ID: Date: Thu, 5 Jun 2025 08:44:09 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm/hugetlb: remove unnecessary holding of hugetlb_lock To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, muchun.song@linux.dev, osalvador@suse.de, liuzixing@hygon.cn References: <1748317010-16272-1-git-send-email-yangge1116@126.com> <20250604154754.a30e327c3f1640173c8b9cb8@linux-foundation.org> From: Ge Yang In-Reply-To: <20250604154754.a30e327c3f1640173c8b9cb8@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wD31wtZ6EBox0ZuBA--.54588S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7Zw18KFy3Cr1ruF45WFyUKFg_yoW8AryrpF yjkF90kF4DJ3yqkw4xtr4rAF1rZws8Xa45trZ5JFWY9rs8XF92gFsrZw1qyay8Crn3Xw4I qFWjgrWqqFn0y3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jbHUDUUUUU= X-Originating-IP: [112.64.138.194] X-CM-SenderInfo: 51dqwwjhrrila6rslhhfrp/1tbidQdjG2hA5Jtt0wAAsj X-Rspamd-Queue-Id: 52E37C0004 X-Stat-Signature: 6hya4n46r8oswis637eipd33kmjnipp1 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1749084257-949329 X-HE-Meta: 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 84rBOyld 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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: 在 2025/6/5 6:47, Andrew Morton 写道: > On Tue, 27 May 2025 11:36:50 +0800 yangge1116@126.com wrote: > >> From: Ge Yang >> >> In the isolate_or_dissolve_huge_folio() function, after acquiring the >> hugetlb_lock, it is only for the purpose of obtaining the correct hstate, >> which is then passed to the alloc_and_dissolve_hugetlb_folio() function. >> >> The alloc_and_dissolve_hugetlb_folio() function itself also acquires the >> hugetlb_lock. We can have the alloc_and_dissolve_hugetlb_folio() function >> obtain the hstate by itself, so that the isolate_or_dissolve_huge_folio() >> function no longer needs to acquire the hugetlb_lock. In addition, we keep >> the folio_test_hugetlb() check within the isolate_or_dissolve_huge_folio() >> function. By doing so, we can avoid disrupting the normal path by vainly >> holding the hugetlb_lock. >> >> The replace_free_hugepage_folios() function has the same issue, and we >> should address it as well. >> > > This change addresses a possible performance issue which was introduced > by 113ed54ad276 ("mm/hugetlb: fix kernel NULL pointer dereference when > replacing free hugetlb folios"). 113ed54ad276 was added recently and > was cc:stable. > > David said: > https://lkml.kernel.org/r/87521d93-cc03-480d-a2ef-3ef8c84481c9@redhat.com > > > Question is, will that bugfix's performance impact be sufficiently > serious for us to also backport this new patch? In some low-probability scenarios, there could be severe impacts. For example, when multiple CPUs execute the replace_free_hugepage_folios() function simultaneously. It seems that we need to backport this new patch. Thank you.