diff mbox series

[v2,06/35] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT

Message ID	20220128131006.67712-7-michel@lespinasse.org (mailing list archive)
State	New
Headers	show Return-Path: <owner-linux-mm@kvack.org> From: Michel Lespinasse <michel@lespinasse.org> To: Linux-MM <linux-mm@kvack.org>, linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org> Cc: kernel-team@fb.com, Laurent Dufour <ldufour@linux.ibm.com>, Jerome Glisse <jglisse@google.com>, Peter Zijlstra <peterz@infradead.org>, Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>, Davidlohr Bueso <dave@stgolabs.net>, Matthew Wilcox <willy@infradead.org>, Liam Howlett <liam.howlett@oracle.com>, Rik van Riel <riel@surriel.com>, Paul McKenney <paulmck@kernel.org>, Song Liu <songliubraving@fb.com>, Suren Baghdasaryan <surenb@google.com>, Minchan Kim <minchan@google.com>, Joel Fernandes <joelaf@google.com>, David Rientjes <rientjes@google.com>, Axel Rasmussen <axelrasmussen@google.com>, Andy Lutomirski <luto@kernel.org>, Michel Lespinasse <michel@lespinasse.org> Subject: [PATCH v2 06/35] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Date: Fri, 28 Jan 2022 05:09:37 -0800 Message-Id: <20220128131006.67712-7-michel@lespinasse.org> In-Reply-To: <20220128131006.67712-1-michel@lespinasse.org> References: <20220128131006.67712-1-michel@lespinasse.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	Speculative page faults \| expand [v2,00/35] Speculative page faults [v2,01/35] mm: export dump_mm [v2,02/35] mmap locking API: mmap_lock_is_contended returns a bool [v2,03/35] mmap locking API: name the return values [v2,04/35] do_anonymous_page: use update_mmu_tlb() [v2,05/35] do_anonymous_page: reduce code duplication [v2,06/35] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT [v2,07/35] x86/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT [v2,08/35] mm: add FAULT_FLAG_SPECULATIVE flag [v2,09/35] mm: add do_handle_mm_fault() [v2,10/35] mm: add per-mm mmap sequence counter for speculative page fault handling. [v2,11/35] mm: rcu safe vma freeing [v2,12/35] mm: separate mmap locked assertion from find_vma [v2,13/35] x86/mm: attempt speculative mm faults first [v2,14/35] mm: add speculative_page_walk_begin() and speculative_page_walk_end() [v2,15/35] mm: refactor __handle_mm_fault() / handle_pte_fault() [v2,16/35] mm: implement speculative handling in __handle_mm_fault(). [v2,17/35] mm: add pte_map_lock() and pte_spinlock() [v2,18/35] mm: implement speculative handling in do_anonymous_page() [v2,19/35] mm: enable speculative fault handling through do_anonymous_page() [v2,20/35] mm: implement speculative handling in do_numa_page() [v2,21/35] mm: enable speculative fault handling in do_numa_page() [v2,22/35] percpu-rwsem: enable percpu_sem destruction in atomic context [v2,23/35] mm: add mmu_notifier_lock [v2,24/35] mm: write lock mmu_notifier_lock when registering mmu notifiers [v2,25/35] mm: add mmu_notifier_trylock() and mmu_notifier_unlock() [v2,26/35] mm: implement speculative handling in wp_page_copy() [v2,27/35] mm: implement and enable speculative fault handling in handle_pte_fault() [v2,28/35] mm: disable speculative faults for single threaded user space [v2,29/35] mm: disable rcu safe vma freeing for single threaded user space [v2,30/35] mm: create new include/linux/vm_event.h header file [v2,31/35] mm: anon spf statistics [v2,32/35] arm64/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT [v2,33/35] arm64/mm: attempt speculative mm faults first [v2,34/35] powerpc/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT [v2,35/35] powerpc/mm: attempt speculative mm faults first

Commit Message

Michel Lespinasse Jan. 28, 2022, 1:09 p.m. UTC

This configuration variable will be used to build the code needed to
handle speculative page fault.

This is enabled by default on supported architectures with SMP and MMU set.

The architecture support is needed since the speculative page fault handler
is called from the architecture's page faulting code, and some code has to
be added there to try speculative fault handling first.

Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
---
 mm/Kconfig | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff mbox series

Patch

diff --git a/mm/Kconfig b/mm/Kconfig
index 3326ee3903f3..d304fca0f293 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -894,4 +894,26 @@  config ANON_VMA_NAME
 
 source "mm/damon/Kconfig"
 
+config ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
+       def_bool n
+
+config SPECULATIVE_PAGE_FAULT
+	bool "Speculative page faults"
+	default y
+	depends on ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT && MMU && SMP
+	help
+	  Try to handle user space page faults without holding the mmap lock.
+
+	  Instead of blocking writers through the use of mmap lock,
+	  the page fault handler merely verifies, at the end of the page
+	  fault, that no writers have been running concurrently with it.
+
+	  In high concurrency situations, the speculative fault handler
+	  gains a throughput advantage by avoiding having to update the
+	  mmap lock reader count.
+
+	  If the check fails due to a concurrent writer, or due to hitting
+	  an unsupported case, the fault handler falls back to classical
+	  processing using the mmap read lock.
+
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