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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id fu22-20020a05622a5d9600b003be56bdd3b1sm12114385qtb.92.2023.03.08.13.56.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Mar 2023 13:56:10 -0800 (PST) Date: Wed, 8 Mar 2023 16:56:09 -0500 From: Peter Xu To: James Houghton Cc: Mike Kravetz , Hugh Dickins , Muchun Song , "Matthew Wilcox (Oracle)" , Andrew Morton , "Kirill A . Shutemov" , David Hildenbrand , David Rientjes , Axel Rasmussen , Jiaqi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: rmap: make hugetlb pages participate in _nr_pages_mapped Message-ID: References: <20230306230004.1387007-1-jthoughton@google.com> <20230306230004.1387007-2-jthoughton@google.com> <20230307215420.GA59222@monkey> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5750714000F X-Rspam-User: X-Stat-Signature: zjfujcis6k7of1ui17supx8qojatg4sm X-HE-Tag: 1678312574-247737 X-HE-Meta: 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 6S5IZbt6 hj7u5YWZyVylSL7ibPXq/xvQLDHe+O1O4IBRIzRU8zxPthN6Li6k01rtnarmXUgALVZ9rqtwTjeqqx3WWg8TbnHDPaXxIebMqVXKGxXy5RhK57t0QO0s4A5UpOG9PaQLnD4rDXwxdR8NNqTk76tR1GEEzEapIJ1ZBHNycyrNZCzj78d+9AdXGN2rvdk4Kt1jEgJOXDSqq4KVkH/opCg9IoP0/Imlb5So7JeEi3XjwDSdKYSQGyl1VgxpPsjD8Zl0T0pYVoXjRTRvDFY1xIrqYMyrV3AENh7TfMz3RO/vEfAX3LmWh9d72vC+YkQS+9fZ4L9V71Zm+ABzByZrSi1hGe8ZbeTkLO0Eyc4mMd70LU6AD+7qVSX6JPE1ESkDZIYKyDKG4K3GUc7hvifbbkaOgEO46nKY2yqqkds5LSxUWB2WO/KU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 07, 2023 at 04:36:51PM -0800, James Houghton wrote: > > > if (likely(!compound)) { > > > + if (unlikely(folio_test_hugetlb(folio))) > > > + VM_BUG_ON_PAGE(HPageVmemmapOptimized(&folio->page), > > > + page); How about moving folio_test_hugetlb() into the BUG_ON()? VM_BUG_ON_PAGE(folio_test_hugetlb(folio) && HPageVmemmapOptimized(&folio->page), page); Note that BUG_ON() already contains an "unlikely". > > > first = atomic_inc_and_test(&page->_mapcount); > > > nr = first; > > > if (first && folio_test_large(folio)) { > > > nr = atomic_inc_return_relaxed(mapped); > > > nr = (nr < COMPOUND_MAPPED); > > > } > > > - } else if (folio_test_pmd_mappable(folio)) { > > > - /* That test is redundant: it's for safety or to optimize out */ > > > > I 'think' removing this check is OK. It would seem that the caller > > knows if the folio is mappable. If we want a similar test, we might be > > able to use something like: > > > > arch_hugetlb_valid_size(folio_size(folio)) > > > > Ack. I think leaving the check(s) removed is fine. Would it still be good to keep that as another BUG_ON()? -- Peter Xu