From: "Andy Lutomirski" <luto@kernel.org>
To: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "David Hildenbrand" <david@redhat.com>,
"Chih-En Lin" <shiyn.lin@gmail.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
linux-mm@kvack.org, "Ingo Molnar" <mingo@redhat.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
"Daniel Bristot de Oliveira" <bristot@redhat.com>,
"Christian Brauner" <brauner@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
"William Kucharski" <william.kucharski@oracle.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Yunsheng Lin" <linyunsheng@huawei.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Suren Baghdasaryan" <surenb@google.com>,
"Colin Cross" <ccross@google.com>,
"Feng Tang" <feng.tang@intel.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"Mike Rapoport" <rppt@kernel.org>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
"Daniel Axtens" <dja@axtens.net>,
"Jonathan Marek" <jonathan@marek.ca>,
"Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Pasha Tatashin" <pasha.tatashin@soleen.com>,
"Peter Xu" <peterx@redhat.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Fenghua Yu" <fenghua.yu@intel.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Kaiyang Zhao" <zhao776@purdue.edu>,
"Huichun Feng" <foxhoundsk.tw@gmail.com>,
"Jim Huang" <jserv.tw@gmail.com>
Subject: Re: [RFC PATCH 0/6] Introduce Copy-On-Write to Page Table
Date: Sun, 22 May 2022 08:20:05 -0700 [thread overview]
Message-ID: <c82ac102-7935-4b07-9d8c-82a2efe59956@www.fastmail.com> (raw)
In-Reply-To: <YomERsAM3gF7XxRZ@casper.infradead.org>
On Sat, May 21, 2022, at 5:31 PM, Matthew Wilcox wrote:
> On Sat, May 21, 2022 at 03:19:24PM -0700, Andy Lutomirski wrote:
>> I can see a rather different use for this type of shared-pagetable
>> technology, though: monstrous MAP_SHARED mappings. For database and some VM
>> users, multiple processes will map the same file. If there was a way to
>> ensure appropriate alignment (or at least encourage it) and a way to handle
>> mappings that don't cover the whole file, then having multiple mappings
>> share the same page tables could be a decent efficiently gain. This doesn't
>> even need COW -- it's "just" pagetable sharing.
>
> The mshare proposal did not get a warm reception at LSFMM ;-(
>
> The conceptual model doesn't seem to work for the MM developers who were
> in the room. "Fear" was the most-used word. Not sure how we're going
> to get to a model of sharing page tables that doesn't scare people.
FWIW, I didn’t like mshare. mshare was weird: it seemed to have one mm own some page tables and other mms share them. I’m talking about having a *file* own page tables and mms map them. This seems less fear-inducing to me. Circular dependencies are impossible, mmap calls don’t need to propagate, etc.
It would still be quite a change, though.
next prev parent reply other threads:[~2022-05-22 21:19 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-19 18:31 Chih-En Lin
2022-05-19 18:31 ` [RFC PATCH 1/6] mm: Add a new mm flag for Copy-On-Write PTE table Chih-En Lin
2022-05-19 18:31 ` [RFC PATCH 2/6] mm: clone3: Add CLONE_COW_PGTABLE flag Chih-En Lin
2022-05-20 14:13 ` Christophe Leroy
2022-05-21 3:50 ` Chih-En Lin
2022-05-19 18:31 ` [RFC PATCH 3/6] mm, pgtable: Add ownership for the PTE table Chih-En Lin
2022-05-20 14:15 ` Christophe Leroy
2022-05-21 4:03 ` Chih-En Lin
2022-05-21 4:02 ` Matthew Wilcox
2022-05-21 5:01 ` Chih-En Lin
2022-05-19 18:31 ` [RFC PATCH 4/6] mm: Add COW PTE fallback function Chih-En Lin
2022-05-20 14:21 ` Christophe Leroy
2022-05-21 4:15 ` Chih-En Lin
2022-05-19 18:31 ` [RFC PATCH 5/6] mm, pgtable: Add the reference counter for COW PTE Chih-En Lin
2022-05-20 14:30 ` Christophe Leroy
2022-05-21 4:22 ` Chih-En Lin
2022-05-21 4:08 ` Matthew Wilcox
2022-05-21 5:10 ` Chih-En Lin
2022-05-19 18:31 ` [RFC PATCH 6/6] mm: Expand Copy-On-Write to PTE table Chih-En Lin
2022-05-20 14:49 ` Christophe Leroy
2022-05-21 4:38 ` Chih-En Lin
2022-05-21 8:59 ` [External] [RFC PATCH 0/6] Introduce Copy-On-Write to Page Table Qi Zheng
2022-05-21 19:08 ` Chih-En Lin
2022-05-21 16:07 ` David Hildenbrand
2022-05-21 18:50 ` Chih-En Lin
2022-05-21 20:28 ` David Hildenbrand
2022-05-21 20:12 ` Matthew Wilcox
2022-05-21 20:22 ` David Hildenbrand
2022-05-21 22:19 ` Andy Lutomirski
2022-05-22 0:31 ` Matthew Wilcox
2022-05-22 15:20 ` Andy Lutomirski [this message]
2022-05-22 19:40 ` Matthew Wilcox
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