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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id bq35-20020a05620a46a300b00704c9015e68sm11574195qkb.116.2023.01.12.13.33.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jan 2023 13:33:14 -0800 (PST) Date: Thu, 12 Jan 2023 16:33:13 -0500 From: Peter Xu To: James Houghton Cc: Mike Kravetz , Muchun Song , David Hildenbrand , David Rientjes , Axel Rasmussen , Mina Almasry , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 21/46] hugetlb: use struct hugetlb_pte for walk_hugetlb_range Message-ID: References: <20230105101844.1893104-1-jthoughton@google.com> <20230105101844.1893104-22-jthoughton@google.com> 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: rspam05 X-Rspamd-Queue-Id: 19C9C40018 X-Stat-Signature: hedo6dy94wk3bogsc11z9r4ytkx9krmg X-Rspam-User: X-HE-Tag: 1673559198-474296 X-HE-Meta: U2FsdGVkX18fr9pyfV/BHI54Gq9Re4Z6zjTJmrjKIbBxOfRq2uLIlIItmQJsIpJc56ohWBPdJJoUHO0wf7L9LtZFClyxOZU+Xsc8uLINnnmkJ9iiqZkBf41iUotOMK1/tbOW85lxEQp6rodUoV+5E51l8XiWf4e1ZCpB2BMZCl5uJFafdMKxfol3UZD8xSFbUmEHaUzTm80yAGpHsMpwapk942pxXPKS4upwPy7qZL3ZiZMF8dtZKSzRjTZFwSVutpdy94eWwFZ/1u7pC/G2lesSUArJvqHB/+b1Eubk8rUbhXYvMpV2QQg2u2rEcrvvkCIBMDBYUuVJ91EbBbQgoH08+p/0slkh9SFuubHcqd3xU68U7vvE3t5+5l/b1rTPwV1pBLvxJGyoLSgR2VqOoBkAAsBrXBPxdHyiYdIz5/6PQdxhNiCAKVYgovkujidgAEk0kwkv+895vKN3C7IMnnGQr4b6fYFUc/g6nsRGOSz7MpYVFrVt0gzYyFmRAn6N9JcF0c1E6D7VOgdsXDNV31dOw+fEUyDKT9ULeguYNvGqbbe055dWDctHA6JI+ysftEHdSDCu1c86Fk2iVEEK1y+ONn11s+BidlEjJlf+F3s90XQ5FyzAtSRW+stN/PWjrNI+NSqGsQI7A/GdxM4Ob2hNvE2H+5p5kFd0x1bHbnByIzUk1UAdVulZUnfTlN1l68G2gKO7oz64ArwrNWNeIvDMeMNEtTINJ073kNAaZg6q+cbyn+9sAjxvDB+rpgvaf6lBO+xb6K/x5i6HTKk2escZex3kf7cqej2/zArcZF82lGMPlLmi7n477CLUrh/lnHOhRLLsHo2XWkVFUwEnm502PHjYR6Uuao8Z1MTknPRn1BWxZRb6XV7pjY1rz1qawkL+tUBuUbcRTf2THmoEPgGd0oScnaknHweI/oXWYSUcuoGIf97TjLjzNqkMlEFrx7O17llJpMROwhNdh3q uUAekUD0 ZazPN9VoeqYU17iL6O+GdG17r9CVgB2rDSSK+SMlaiT93yJh+Z+9MEJKAcWDCqvA+lv8SLiCvCZOZoP9sOiIj9RZsJa60fOz9HbKPF8NLHDMjcav5V4hcMbM2CuyOK5zuHf+u47Xwd9xUOjSbLr1i4QDvTw== 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 Thu, Jan 12, 2023 at 04:17:52PM -0500, James Houghton wrote: > I'll look into it, but doing it this way will use _mapcount, so we > won't be able to use the vmemmap optimization. I think even if we do > use Hugh's approach, refcount is still being kept on the head page, so > there's still an overflow risk there (but maybe I am > misunderstanding). Could you remind me what's the issue if using refcount on the small pages rather than the head (assuming vmemmap still can be disabled)? Thanks, -- Peter Xu