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Wed, 09 Dec 2020 05:10:42 -0500 X-MC-Unique: F-PKDTCLPnu8Iu_PevaM0A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C4C67B8101; Wed, 9 Dec 2020 10:10:37 +0000 (UTC) Received: from [10.36.114.167] (ovpn-114-167.ams2.redhat.com [10.36.114.167]) by smtp.corp.redhat.com (Postfix) with ESMTP id B53EA6E41C; Wed, 9 Dec 2020 10:10:31 +0000 (UTC) Subject: Re: [External] Re: [PATCH v7 06/15] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two From: David Hildenbrand To: Muchun Song Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Oscar Salvador , Michal Hocko , "Song Bao Hua (Barry Song)" , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel References: <20201130151838.11208-1-songmuchun@bytedance.com> <20201130151838.11208-7-songmuchun@bytedance.com> <4b8a9389-1704-4d8c-ec58-abd753814dd9@redhat.com> Organization: Red Hat GmbH Message-ID: Date: Wed, 9 Dec 2020 11:10:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <4b8a9389-1704-4d8c-ec58-abd753814dd9@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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: On 09.12.20 11:06, David Hildenbrand wrote: > On 09.12.20 11:03, Muchun Song wrote: >> On Wed, Dec 9, 2020 at 5:57 PM David Hildenbrand wrote: >>> >>> On 30.11.20 16:18, Muchun Song wrote: >>>> We only can free the tail vmemmap pages of HugeTLB to the buddy allocator >>>> when the size of struct page is a power of two. >>>> >>>> Signed-off-by: Muchun Song >>>> --- >>>> mm/hugetlb_vmemmap.c | 5 +++++ >>>> 1 file changed, 5 insertions(+) >>>> >>>> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c >>>> index 51152e258f39..ad8fc61ea273 100644 >>>> --- a/mm/hugetlb_vmemmap.c >>>> +++ b/mm/hugetlb_vmemmap.c >>>> @@ -111,6 +111,11 @@ void __init hugetlb_vmemmap_init(struct hstate *h) >>>> unsigned int nr_pages = pages_per_huge_page(h); >>>> unsigned int vmemmap_pages; >>>> >>>> + if (!is_power_of_2(sizeof(struct page))) { >>>> + pr_info("disable freeing vmemmap pages for %s\n", h->name); >>> >>> I'd just drop that pr_info(). Users are able to observe that it's >>> working (below), so they are able to identify that it's not working as well. >> >> The below is just a pr_debug. Do you suggest converting it to pr_info? > > Good question. I wonder if users really have to know in most cases. > Maybe pr_debug() is good enough in environments where we want to debug > why stuff is not working as expected. > Oh, another thought, can we glue availability of HUGETLB_PAGE_FREE_VMEMMAP (or a new define based on the config and the size of a stuct page) to the size of struct page somehow? I mean, it's known at compile time that this will never work. -- Thanks, David / dhildenb