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[142.68.25.194]) by smtp.gmail.com with ESMTPSA id r15-20020a05620a03cf00b0074e0951c7e7sm6340805qkm.28.2023.06.29.08.22.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Jun 2023 08:22:24 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1qEtTU-009snj-1H; Thu, 29 Jun 2023 12:22:24 -0300 Date: Thu, 29 Jun 2023 12:22:24 -0300 From: Jason Gunthorpe To: Hugh Dickins Cc: Gerald Schaefer , Andrew Morton , Vasily Gorbik , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Russell King , "David S. Miller" , Michael Ellerman , "Aneesh Kumar K.V" , Heiko Carstens , Christian Borntraeger , Claudio Imbrenda , Alexander Gordeev , Jann Horn , Vishal Moola , Vlastimil Babka , linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 07/12] s390: add pte_free_defer() for pgtables sharing page Message-ID: References: <54cb04f-3762-987f-8294-91dafd8ebfb0@google.com> <20230628211624.531cdc58@thinkpad-T15> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8503F80013 X-Stat-Signature: kmzfn1yisji65g54tkh85qdr9tkciozx X-HE-Tag: 1688052146-790281 X-HE-Meta: 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 7q1fuhyV +5Tl+qdytVbykhC9B5MVqXhn/XKJzdQw/6f4wOeQkT42Tx9E3L8Du9C1zLNcoHMPS3cLLDToTueP5d8Xxf7iG4yBjpH9wh7yLD7n59sFpLPK/kQLG7bGOZV2Bp1mKgH1mFqWOh67dr4uxBBpMLwiA+xAY/0s3ldKvwujd7yxKeV/VZ735qHpuVHL+diXpWVsfyKJ5CZpew+9ddWV2BXg49m89+DjyA8OXR+keZowRaydvC1TykxaUpWlVa0Es2/Pi8u3da7VQqxAywuIGyqapYXXSx4qm0jN6d1OMin1gaJ0dJCQCG7wwZOxQ/rv7N8iOq0oOrFucAda9Z2IrRGXlMYPdcswhGUbzNAagaRAeZNkHMK7RQdvo+Vytnj12e6Mo224/6FFspaZpbqa2tsEStpSAD1dWHuVZSBAecykiIRUowEW5doOvGoi0aw== 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, Jun 28, 2023 at 10:08:08PM -0700, Hugh Dickins wrote: > On Wed, 28 Jun 2023, Gerald Schaefer wrote: > > > > As discussed in the other thread, we would rather go with less complexity, > > possibly switching to an approach w/o the list and fragment re-use in the > > future. For now, as a first step in that direction, we can try with not > > adding fragments back only for pte_free_defer(). Here is an adjusted > > version of your patch, copying most of your pte_free_defer() logic and > > also description, tested with LTP and all three of your patch series applied: > > Thanks, Gerald: I don't mind abandoning my 13/12 SLAB_TYPESAFE_BY_RCU > patch (posted with fewer Cc's to the s390 list last week), and switching > to your simpler who-cares-if-we-sometimes-don't-make-maximal-use-of-page > patch. > > But I didn't get deep enough into it today to confirm it - and disappointed > that you've found it necessary to play with pt_frag_refcount in addition to > _refcount and HH bits. No real problem with that, but my instinct says it > should be simpler. Is there any reason it should be any different at all from what PPC is doing? I still think the right thing to do here is make the PPC code common (with Hugh's proposed RCU modification) and just use it in both arches.... Jason