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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1r44e9-00BEGO-NL; Fri, 17 Nov 2023 19:36:57 +0000 Date: Fri, 17 Nov 2023 19:36:57 +0000 From: Matthew Wilcox To: Barry Song <21cnbao@gmail.com> Cc: David Hildenbrand , steven.price@arm.com, akpm@linux-foundation.org, ryan.roberts@arm.com, catalin.marinas@arm.com, will@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, shy828301@gmail.com, v-songbaohua@oppo.com, wangkefeng.wang@huawei.com, xiang@kernel.org, ying.huang@intel.com, yuzhao@google.com Subject: Re: [RFC V3 PATCH] arm64: mm: swap: save and restore mte tags for large folios Message-ID: References: <20231114014313.67232-1-v-songbaohua@oppo.com> <864489b3-5d85-4145-b5bb-5d8a74b9b92d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 82EA48000B X-Stat-Signature: 1iino8qt5835kmshssmfoea9qc9fk8dn X-Rspam-User: X-HE-Tag: 1700249833-383 X-HE-Meta: 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 RkkElpyR Wlp13ws5ZBA+KSYDTn2aq7nFK8n+01MHcI182rvOMHgQkzZkRQmAeUl6vMOh14mI6tVyl1e2UsLK04rjuPNooGH7VtSl9BE45PrttltZe2EHPMS6ub2YsVqEVWV2byT4wNWo8MH2oCnquNuw= 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: On Fri, Nov 17, 2023 at 07:47:00AM +0800, Barry Song wrote: > This has been discussed. Steven, Ryan and I all don't think this is a good > option. in case we have a large folio with 16 basepages, as do_swap_page > can only map one base page for each page fault, that means we have > to restore 16(tags we restore in each page fault) * 16(the times of page faults) > for this large folio. That doesn't seem all that hard to fix? Call set_ptes() instead of set_pte_at(). The biggest thing, I guess, is making sure that all the PTEs you're going to set up are still pte_none().