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Wed, 09 Dec 2020 02:03:39 -0800 (PST) MIME-Version: 1.0 References: <20201130151838.11208-1-songmuchun@bytedance.com> <20201130151838.11208-7-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Wed, 9 Dec 2020 18:03:02 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v7 06/15] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two To: David Hildenbrand 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 Content-Type: text/plain; charset="UTF-8" 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 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? > > > + return; > > + } > > + > > vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT; > > /* > > * The head page and the first tail page are not to be freed to buddy > > > > Please squash this patch into the enabling patch and add a comment > instead, like > > /* We cannot optimize if a "struct page" crosses page boundaries. */ > Will do. Thanks. > -- > Thanks, > > David / dhildenb > -- Yours, Muchun