Re: [PATCH v11 01/26] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT
On 17/05/2018 18:36, Randy Dunlap wrote: > Hi, > > On 05/17/2018 04:06 AM, Laurent Dufour wrote: >> This configuration variable will be used to build the code needed to >> handle speculative page fault. >> >> By default it is turned off, and activated depending on architecture >> support, ARCH_HAS_PTE_SPECIAL, SMP and MMU. >> >> 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 handle the speculative handler. >> >> The dependency on ARCH_HAS_PTE_SPECIAL is required because vm_normal_page() >> does processing that is not compatible with the speculative handling in the >> case ARCH_HAS_PTE_SPECIAL is not set. >> >> Suggested-by: Thomas Gleixner >> Suggested-by: David Rientjes >> Signed-off-by: Laurent Dufour >> --- >> mm/Kconfig | 22 ++ >> 1 file changed, 22 insertions(+) >> >> diff --git a/mm/Kconfig b/mm/Kconfig >> index 1d0888c5b97a..a38796276113 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -761,3 +761,25 @@ config GUP_BENCHMARK >> >> config ARCH_HAS_PTE_SPECIAL >> bool >> + >> +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 >> + depends on ARCH_HAS_PTE_SPECIAL && MMU && SMP >> + help >> + Try to handle user space page faults without holding the mmap_sem. >> + >> + This should allow better concurrency for massively threaded process > >processes > >> + since the page fault handler will not wait for other threads memory > > thread's > >> + layout change to be done, assuming that this change is done in another >> + part of the process's memory space. This type of page fault is named >> + speculative page fault. >> + >> + If the speculative page fault fails because of a concurrency is > >because a concurrency is > >> + detected or because underlying PMD or PTE tables are not yet >> + allocating, it is failing its processing and a classic page fault > >allocated, the speculative page fault fails and a classic page fault > >> + is then tried. > > > Also, all of the help text (below the "help" line) should be indented by > 1 tab + 2 spaces (in coding-style.rst). Thanks, Randy for reviewing my miserable English grammar. I'll fix that and the indentation.
Re: [PATCH v11 01/26] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT
On 17/05/2018 19:19, Matthew Wilcox wrote: > On Thu, May 17, 2018 at 09:36:00AM -0700, Randy Dunlap wrote: >>> +If the speculative page fault fails because of a concurrency is >> >> because a concurrency is > > While one can use concurrency as a noun, it sounds archaic to me. I'd > rather: > > If the speculative page fault fails because a concurrent modification > is detected or because underlying PMD or PTE tables are not yet Thanks Matthew, I'll do that. > >>> +detected or because underlying PMD or PTE tables are not yet >>> +allocating, it is failing its processing and a classic page fault >> >> allocated, the speculative page fault fails and a classic page fault >> >>> +is then tried. >
Re: [PATCH v11 01/26] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT
On 05/17/2018 10:19 AM, Matthew Wilcox wrote: > On Thu, May 17, 2018 at 09:36:00AM -0700, Randy Dunlap wrote: >>> +If the speculative page fault fails because of a concurrency is >> >> because a concurrency is > > While one can use concurrency as a noun, it sounds archaic to me. I'd > rather: > > If the speculative page fault fails because a concurrent modification > is detected or because underlying PMD or PTE tables are not yet Yeah, OK. >>> +detected or because underlying PMD or PTE tables are not yet >>> +allocating, it is failing its processing and a classic page fault >> >> allocated, the speculative page fault fails and a classic page fault >> >>> +is then tried. -- ~Randy
Re: [PATCH v11 01/26] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT
On Thu, May 17, 2018 at 09:36:00AM -0700, Randy Dunlap wrote: > > +If the speculative page fault fails because of a concurrency is > >because a concurrency is While one can use concurrency as a noun, it sounds archaic to me. I'd rather: If the speculative page fault fails because a concurrent modification is detected or because underlying PMD or PTE tables are not yet > > +detected or because underlying PMD or PTE tables are not yet > > +allocating, it is failing its processing and a classic page fault > >allocated, the speculative page fault fails and a classic page fault > > > +is then tried.
Re: [PATCH v11 01/26] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT
Hi, On 05/17/2018 04:06 AM, Laurent Dufour wrote: > This configuration variable will be used to build the code needed to > handle speculative page fault. > > By default it is turned off, and activated depending on architecture > support, ARCH_HAS_PTE_SPECIAL, SMP and MMU. > > 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 handle the speculative handler. > > The dependency on ARCH_HAS_PTE_SPECIAL is required because vm_normal_page() > does processing that is not compatible with the speculative handling in the > case ARCH_HAS_PTE_SPECIAL is not set. > > Suggested-by: Thomas Gleixner > Suggested-by: David Rientjes > Signed-off-by: Laurent Dufour > --- > mm/Kconfig | 22 ++ > 1 file changed, 22 insertions(+) > > diff --git a/mm/Kconfig b/mm/Kconfig > index 1d0888c5b97a..a38796276113 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -761,3 +761,25 @@ config GUP_BENCHMARK > > config ARCH_HAS_PTE_SPECIAL > bool > + > +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 > + depends on ARCH_HAS_PTE_SPECIAL && MMU && SMP > + help > + Try to handle user space page faults without holding the mmap_sem. > + > + This should allow better concurrency for massively threaded process processes > + since the page fault handler will not wait for other threads memory thread's > + layout change to be done, assuming that this change is done in another > + part of the process's memory space. This type of page fault is named > + speculative page fault. > + > + If the speculative page fault fails because of a concurrency is because a concurrency is > + detected or because underlying PMD or PTE tables are not yet > + allocating, it is failing its processing and a classic page fault allocated, the speculative page fault fails and a classic page fault > + is then tried. Also, all of the help text (below the "help" line) should be indented by 1 tab + 2 spaces (in coding-style.rst). -- ~Randy