From: Michal Hocko <mhocko@kernel.org>
To: Michel Lespinasse <walken@google.com>
Cc: Jan Kara <jack@suse.cz>,
sergey.senozhatsky.work@gmail.com,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will.deacon@arm.com>, linux-mm <linux-mm@kvack.org>,
Paul Mackerras <paulus@samba.org>,
Punit Agrawal <punitagrawal@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
dave@stgolabs.net, Minchan Kim <minchan@kernel.org>,
aneesh.kumar@linux.ibm.com, x86@kernel.org,
Matthew Wilcox <willy@infradead.org>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Ingo Molnar <mingo@redhat.com>,
David Rientjes <rientjes@google.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Haiyan Song <haiyanx.song@intel.com>,
Nick Piggin <npiggin@gmail.com>,
sj38.park@gmail.com, Jerome Glisse <jglisse@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
kemi.wang@intel.com, "Kirill A. Shutemov" <kirill@shutemov.name>,
Thomas Gleixner <tglx@linutronix.de>,
Laurent Dufour <ldufour@linux.ibm.com>,
zhong jiang <zhongjiang@huawei.com>,
Ganesh Mahendran <opensource.ganesh@gmail.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
linuxppc-dev@lists.ozlabs.org,
LKML <linux-kernel@vger.kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
vinayak menon <vinayakm.list@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
haren@linux.vnet.ibm.com
Subject: Re: [PATCH v12 00/31] Speculative page faults
Date: Tue, 23 Apr 2019 12:47:07 +0200 [thread overview]
Message-ID: <20190423104707.GK25106@dhcp22.suse.cz> (raw)
In-Reply-To: <CANN689F1h9XoHPzr_FQY2WfN5bb2TTd6M3HLqoJ-DQuHkNbA7g@mail.gmail.com>
On Mon 22-04-19 14:29:16, Michel Lespinasse wrote:
[...]
> I want to add a note about mmap_sem. In the past there has been
> discussions about replacing it with an interval lock, but these never
> went anywhere because, mostly, of the fact that such mechanisms were
> too expensive to use in the page fault path. I think adding the spf
> mechanism would invite us to revisit this issue - interval locks may
> be a great way to avoid blocking between unrelated mmap_sem writers
> (for example, do not delay stack creation for new threads while a
> large mmap or munmap may be going on), and probably also to handle
> mmap_sem readers that can't easily use the spf mechanism (for example,
> gup callers which make use of the returned vmas). But again that is a
> separate topic to explore which doesn't have to get resolved before
> spf goes in.
Well, I believe we should _really_ re-evaluate the range locking sooner
rather than later. Why? Because it looks like the most straightforward
approach to the mmap_sem contention for most usecases I have heard of
(mostly a mm{unm}ap, mremap standing in the way of page faults).
On a plus side it also makes us think about the current mmap (ab)users
which should lead to an overall code improvements and maintainability.
SPF sounds like a good idea but it is a really big and intrusive surgery
to the #PF path. And more importantly without any real world usecase
numbers which would justify this. That being said I am not opposed to
this change I just think it is a large hammer while we haven't seen
attempts to tackle problems in a simpler way.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-04-23 10:49 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 13:44 [PATCH v12 00/31] Speculative page faults Laurent Dufour
2019-04-16 13:44 ` [PATCH v12 01/31] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Laurent Dufour
2019-04-18 21:47 ` Jerome Glisse
2019-04-23 15:21 ` Laurent Dufour
2019-04-16 13:44 ` [PATCH v12 02/31] x86/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2019-04-18 21:48 ` Jerome Glisse
2019-04-16 13:44 ` [PATCH v12 03/31] powerpc/mm: set ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2019-04-18 21:49 ` Jerome Glisse
2019-04-16 13:44 ` [PATCH v12 04/31] arm64/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2019-04-16 14:27 ` Mark Rutland
2019-04-16 14:31 ` Laurent Dufour
2019-04-16 14:41 ` Mark Rutland
2019-04-18 21:51 ` Jerome Glisse
2019-04-23 15:36 ` Laurent Dufour
2019-04-23 16:19 ` Mark Rutland
2019-04-24 10:34 ` Laurent Dufour
2019-04-16 13:44 ` [PATCH v12 05/31] mm: prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour
2019-04-18 22:04 ` Jerome Glisse
2019-04-23 15:45 ` Laurent Dufour
2019-04-16 13:44 ` [PATCH v12 06/31] mm: introduce pte_spinlock " Laurent Dufour
2019-04-18 22:05 ` Jerome Glisse
2019-04-16 13:44 ` [PATCH v12 07/31] mm: make pte_unmap_same compatible with SPF Laurent Dufour
2019-04-18 22:10 ` Jerome Glisse
2019-04-23 15:43 ` Matthew Wilcox
2019-04-23 15:47 ` Laurent Dufour
2019-04-16 13:44 ` [PATCH v12 08/31] mm: introduce INIT_VMA() Laurent Dufour
2019-04-18 22:22 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 09/31] mm: VMA sequence count Laurent Dufour
2019-04-18 22:48 ` Jerome Glisse
2019-04-19 15:45 ` Laurent Dufour
2019-04-22 15:51 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 10/31] mm: protect VMA modifications using " Laurent Dufour
2019-04-22 19:43 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 11/31] mm: protect mremap() against SPF hanlder Laurent Dufour
2019-04-22 19:51 ` Jerome Glisse
2019-04-23 15:51 ` Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 12/31] mm: protect SPF handler against anon_vma changes Laurent Dufour
2019-04-22 19:53 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 13/31] mm: cache some VMA fields in the vm_fault structure Laurent Dufour
2019-04-22 20:06 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 14/31] mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() Laurent Dufour
2019-04-22 20:09 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 15/31] mm: introduce __lru_cache_add_active_or_unevictable Laurent Dufour
2019-04-22 20:11 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 16/31] mm: introduce __vm_normal_page() Laurent Dufour
2019-04-22 20:15 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 17/31] mm: introduce __page_add_new_anon_rmap() Laurent Dufour
2019-04-22 20:18 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 18/31] mm: protect against PTE changes done by dup_mmap() Laurent Dufour
2019-04-22 20:32 ` Jerome Glisse
2019-04-24 10:33 ` Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 19/31] mm: protect the RB tree with a sequence lock Laurent Dufour
2019-04-22 20:33 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 20/31] mm: introduce vma reference counter Laurent Dufour
2019-04-22 20:36 ` Jerome Glisse
2019-04-24 14:26 ` Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 21/31] mm: Introduce find_vma_rcu() Laurent Dufour
2019-04-22 20:57 ` Jerome Glisse
2019-04-24 14:39 ` Laurent Dufour
2019-04-23 9:27 ` Peter Zijlstra
2019-04-23 18:13 ` Davidlohr Bueso
2019-04-24 7:57 ` Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 22/31] mm: provide speculative fault infrastructure Laurent Dufour
2019-04-22 21:26 ` Jerome Glisse
2019-04-24 14:56 ` Laurent Dufour
2019-04-24 15:13 ` Jerome Glisse
2019-04-16 13:45 ` [PATCH v12 23/31] mm: don't do swap readahead during speculative page fault Laurent Dufour
2019-04-22 21:36 ` Jerome Glisse
2019-04-24 14:57 ` Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 24/31] mm: adding speculative page fault failure trace events Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 25/31] perf: add a speculative page fault sw event Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 26/31] perf tools: add support for the SPF perf event Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 27/31] mm: add speculative page fault vmstats Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 28/31] x86/mm: add speculative pagefault handling Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 29/31] powerpc/mm: add speculative page fault Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 30/31] arm64/mm: " Laurent Dufour
2019-04-16 13:45 ` [PATCH v12 31/31] mm: Add a speculative page fault switch in sysctl Laurent Dufour
2019-04-22 21:29 ` [PATCH v12 00/31] Speculative page faults Michel Lespinasse
2019-04-23 9:38 ` Peter Zijlstra
2019-04-24 7:33 ` Laurent Dufour
2019-04-27 1:53 ` Michel Lespinasse
2019-04-23 10:47 ` Michal Hocko [this message]
2019-04-23 12:41 ` Matthew Wilcox
2019-04-23 12:48 ` Peter Zijlstra
2019-04-23 13:42 ` Michal Hocko
2019-04-24 18:01 ` Laurent Dufour
2019-04-27 6:00 ` Michel Lespinasse
2019-04-23 11:35 ` Anshuman Khandual
2019-06-06 6:51 ` Haiyan Song
2019-06-14 8:37 ` Laurent Dufour
2019-06-14 8:44 ` Laurent Dufour
2019-06-20 8:19 ` Haiyan Song
2020-07-06 9:25 ` Chinwen Chang
2020-07-06 12:27 ` Laurent Dufour
2020-07-07 5:31 ` Chinwen Chang
2020-12-14 2:03 ` Joel Fernandes
2020-12-14 9:36 ` Laurent Dufour
2020-12-14 18:10 ` Joel Fernandes
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