| Message ID | 20191009124418.8286-1-joro@8bytes.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] x86/mm: Split vmalloc_sync_all() | expand |
On Wednesday, October 9, 2019 2:44:18 PM CEST Joerg Roedel wrote: > From: Joerg Roedel <jroedel@suse.de> > > Git commit 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in > __purge_vmap_area_lazy()") introduced a call to vmalloc_sync_all() in > the vunmap() code-path. While this change was necessary to maintain > correctness on x86-32-pae kernels, it also adds additional cycles for > architectures that don't need it. > > Specifically on x86-64 with CONFIG_VMAP_STACK=y some people reported > severe performance regressions in micro-benchmarks because it now also > calls the x86-64 implementation of vmalloc_sync_all() on vunmap(). But > the vmalloc_sync_all() implementation on x86-64 is only needed for > newly created mappings. > > To avoid the unnecessary work on x86-64 and to gain the performance > back, split up vmalloc_sync_all() into two functions: > > * vmalloc_sync_mappings(), and > * vmalloc_sync_unmappings() > > Most call-sites to vmalloc_sync_all() only care about new mappings > being synchronized. The only exception is the new call-site > added in the above mentioned commit. > > Reported-by: kernel test robot <oliver.sang@intel.com> > Fixes: 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") > Signed-off-by: Joerg Roedel <jroedel@suse.de> For the GHES bits Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > Changes to initial post: > - Added comments to x86-64 version of > vmalloc_sync_[un]mappings() as suggested by Dave > Hansen. > > arch/x86/mm/fault.c | 26 ++++++++++++++++++++++++-- > drivers/acpi/apei/ghes.c | 2 +- > include/linux/vmalloc.h | 5 +++-- > kernel/notifier.c | 2 +- > mm/nommu.c | 10 +++++++--- > mm/vmalloc.c | 11 +++++++---- > 6 files changed, 43 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index 9ceacd1156db..94174361f524 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -189,7 +189,7 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) > return pmd_k; > } > > -void vmalloc_sync_all(void) > +static void vmalloc_sync(void) > { > unsigned long address; > > @@ -216,6 +216,16 @@ void vmalloc_sync_all(void) > } > } > > +void vmalloc_sync_mappings(void) > +{ > + vmalloc_sync(); > +} > + > +void vmalloc_sync_unmappings(void) > +{ > + vmalloc_sync(); > +} > + > /* > * 32-bit: > * > @@ -318,11 +328,23 @@ static void dump_pagetable(unsigned long address) > > #else /* CONFIG_X86_64: */ > > -void vmalloc_sync_all(void) > +void vmalloc_sync_mappings(void) > { > + /* > + * 64-bit mappings might allocate new p4d/pud pages > + * that need to be propagated to all tasks' PGDs. > + */ > sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); > } > > +void vmalloc_sync_unmappings(void) > +{ > + /* > + * Unmappings never allocate or free p4d/pud pages. > + * No work is required here. > + */ > +} > + > /* > * 64-bit: > * > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c > index 777f6f7122b4..e0d82fab1f44 100644 > --- a/drivers/acpi/apei/ghes.c > +++ b/drivers/acpi/apei/ghes.c > @@ -171,7 +171,7 @@ int ghes_estatus_pool_init(int num_ghes) > * New allocation must be visible in all pgd before it can be found by > * an NMI allocating from the pool. > */ > - vmalloc_sync_all(); > + vmalloc_sync_mappings(); > > rc = gen_pool_add(ghes_estatus_pool, addr, PAGE_ALIGN(len), -1); > if (rc) > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 4e7809408073..decac0790fc1 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -126,8 +126,9 @@ extern int remap_vmalloc_range_partial(struct vm_area_struct *vma, > > extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, > unsigned long pgoff); > -void vmalloc_sync_all(void); > - > +void vmalloc_sync_mappings(void); > +void vmalloc_sync_unmappings(void); > + > /* > * Lowlevel-APIs (not for driver use!) > */ > diff --git a/kernel/notifier.c b/kernel/notifier.c > index d9f5081d578d..157d7c29f720 100644 > --- a/kernel/notifier.c > +++ b/kernel/notifier.c > @@ -554,7 +554,7 @@ NOKPROBE_SYMBOL(notify_die); > > int register_die_notifier(struct notifier_block *nb) > { > - vmalloc_sync_all(); > + vmalloc_sync_mappings(); > return atomic_notifier_chain_register(&die_chain, nb); > } > EXPORT_SYMBOL_GPL(register_die_notifier); > diff --git a/mm/nommu.c b/mm/nommu.c > index 99b7ec318824..3b67bd20c2af 100644 > --- a/mm/nommu.c > +++ b/mm/nommu.c > @@ -359,10 +359,14 @@ void vm_unmap_aliases(void) > EXPORT_SYMBOL_GPL(vm_unmap_aliases); > > /* > - * Implement a stub for vmalloc_sync_all() if the architecture chose not to > - * have one. > + * Implement a stub for vmalloc_sync_[un]mapping() if the architecture > + * chose not to have one. > */ > -void __weak vmalloc_sync_all(void) > +void __weak vmalloc_sync_mappings(void) > +{ > +} > + > +void __weak vmalloc_sync_unmappings(void) > { > } > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a3c70e275f4e..c0be707db434 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1259,7 +1259,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > * First make sure the mappings are removed from all page-tables > * before they are freed. > */ > - vmalloc_sync_all(); > + vmalloc_sync_unmappings(); > > /* > * TODO: to calculate a flush range without looping. > @@ -3050,16 +3050,19 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, > EXPORT_SYMBOL(remap_vmalloc_range); > > /* > - * Implement a stub for vmalloc_sync_all() if the architecture chose not to > - * have one. > + * Implement stubs for vmalloc_sync_[un]mappings () if the architecture chose > + * not to have one. > * > * The purpose of this function is to make sure the vmalloc area > * mappings are identical in all page-tables in the system. > */ > -void __weak vmalloc_sync_all(void) > +void __weak vmalloc_sync_mappings(void) > { > } > > +void __weak vmalloc_sync_unmappings(void) > +{ > +} > > static int f(pte_t *pte, unsigned long addr, void *data) > { >
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9ceacd1156db..94174361f524 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -189,7 +189,7 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) return pmd_k; } -void vmalloc_sync_all(void) +static void vmalloc_sync(void) { unsigned long address; @@ -216,6 +216,16 @@ void vmalloc_sync_all(void) } } +void vmalloc_sync_mappings(void) +{ + vmalloc_sync(); +} + +void vmalloc_sync_unmappings(void) +{ + vmalloc_sync(); +} + /* * 32-bit: * @@ -318,11 +328,23 @@ static void dump_pagetable(unsigned long address) #else /* CONFIG_X86_64: */ -void vmalloc_sync_all(void) +void vmalloc_sync_mappings(void) { + /* + * 64-bit mappings might allocate new p4d/pud pages + * that need to be propagated to all tasks' PGDs. + */ sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); } +void vmalloc_sync_unmappings(void) +{ + /* + * Unmappings never allocate or free p4d/pud pages. + * No work is required here. + */ +} + /* * 64-bit: * diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index 777f6f7122b4..e0d82fab1f44 100644 --- a/drivers/acpi/apei/ghes.c +++ b/drivers/acpi/apei/ghes.c @@ -171,7 +171,7 @@ int ghes_estatus_pool_init(int num_ghes) * New allocation must be visible in all pgd before it can be found by * an NMI allocating from the pool. */ - vmalloc_sync_all(); + vmalloc_sync_mappings(); rc = gen_pool_add(ghes_estatus_pool, addr, PAGE_ALIGN(len), -1); if (rc) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 4e7809408073..decac0790fc1 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -126,8 +126,9 @@ extern int remap_vmalloc_range_partial(struct vm_area_struct *vma, extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, unsigned long pgoff); -void vmalloc_sync_all(void); - +void vmalloc_sync_mappings(void); +void vmalloc_sync_unmappings(void); + /* * Lowlevel-APIs (not for driver use!) */ diff --git a/kernel/notifier.c b/kernel/notifier.c index d9f5081d578d..157d7c29f720 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -554,7 +554,7 @@ NOKPROBE_SYMBOL(notify_die); int register_die_notifier(struct notifier_block *nb) { - vmalloc_sync_all(); + vmalloc_sync_mappings(); return atomic_notifier_chain_register(&die_chain, nb); } EXPORT_SYMBOL_GPL(register_die_notifier); diff --git a/mm/nommu.c b/mm/nommu.c index 99b7ec318824..3b67bd20c2af 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -359,10 +359,14 @@ void vm_unmap_aliases(void) EXPORT_SYMBOL_GPL(vm_unmap_aliases); /* - * Implement a stub for vmalloc_sync_all() if the architecture chose not to - * have one. + * Implement a stub for vmalloc_sync_[un]mapping() if the architecture + * chose not to have one. */ -void __weak vmalloc_sync_all(void) +void __weak vmalloc_sync_mappings(void) +{ +} + +void __weak vmalloc_sync_unmappings(void) { } diff --git a/mm/vmalloc.c b/mm/vmalloc.c index a3c70e275f4e..c0be707db434 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1259,7 +1259,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) * First make sure the mappings are removed from all page-tables * before they are freed. */ - vmalloc_sync_all(); + vmalloc_sync_unmappings(); /* * TODO: to calculate a flush range without looping. @@ -3050,16 +3050,19 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, EXPORT_SYMBOL(remap_vmalloc_range); /* - * Implement a stub for vmalloc_sync_all() if the architecture chose not to - * have one. + * Implement stubs for vmalloc_sync_[un]mappings () if the architecture chose + * not to have one. * * The purpose of this function is to make sure the vmalloc area * mappings are identical in all page-tables in the system. */ -void __weak vmalloc_sync_all(void) +void __weak vmalloc_sync_mappings(void) { } +void __weak vmalloc_sync_unmappings(void) +{ +} static int f(pte_t *pte, unsigned long addr, void *data) {