> commit 37b83f3fb77a177a2f81ebb8aeaec28c2a46e503 > Author: Arun Sharma <asharma@xxxxxx> > Date: Tue Jan 10 17:02:46 2012 -0800 > > mm: Enable MAP_UNINITIALIZED for archs with mmu > > This enables malloc optimizations where we might > madvise(..,MADV_DONTNEED) a page only to fault it > back at a different virtual address. > > Signed-off-by: Arun Sharma <asharma@xxxxxx> > > diff --git a/include/asm-generic/mman-common.h b/include/asm-generic/mman-common.h > index 787abbb..71e079f 100644 > --- a/include/asm-generic/mman-common.h > +++ b/include/asm-generic/mman-common.h > @@ -19,11 +19,7 @@ > #define MAP_TYPE 0x0f /* Mask for type of mapping */ > #define MAP_FIXED 0x10 /* Interpret addr exactly */ > #define MAP_ANONYMOUS 0x20 /* don't use a file */ > -#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED > -# define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be uninitialized */ > -#else > -# define MAP_UNINITIALIZED 0x0 /* Don't support this flag */ > -#endif > +#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be uninitialized */ > Define MAP_UNINITIALIZED - are you referring to not zeroing out pages before handing them down? Is this safe even between threads. > #define MS_ASYNC 1 /* sync memory asynchronously */ > #define MS_INVALIDATE 2 /* invalidate the caches */ > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index 3a93f73..04d838e 100644 > --- a/include/linux/highmem.h > +++ b/include/linux/highmem.h > @@ -156,6 +156,11 @@ __alloc_zeroed_user_highpage(gfp_t movableflags, > struct page *page = alloc_page_vma(GFP_HIGHUSER | movableflags, > vma, vaddr); > > +#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED > + if (!vma->vm_file && vma->vm_flags & VM_UNINITIALIZED) > + return page; > +#endif > + > if (page) > clear_user_highpage(page, vaddr); > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 4baadd1..6345c57 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -118,6 +118,8 @@ extern unsigned int kobjsize(const void *objp); > #define VM_SAO 0x20000000 /* Strong Access Ordering (powerpc) */ > #define VM_PFN_AT_MMAP 0x40000000 /* PFNMAP vma that is fully mapped at mmap time */ > #define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */ > +#define VM_UNINITIALIZED VM_SAO /* Steal a powerpc bit for now, since we're out > + bits for 32 bit archs */ Without proper checks if it can be re-used? > > /* Bits set in the VMA until the stack is in its final location */ > #define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ) > diff --git a/include/linux/mman.h b/include/linux/mman.h > index 51647b4..f7d4f60 100644 > --- a/include/linux/mman.h > +++ b/include/linux/mman.h > @@ -88,6 +88,7 @@ calc_vm_flag_bits(unsigned long flags) > return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) | > _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) | > _calc_vm_trans(flags, MAP_EXECUTABLE, VM_EXECUTABLE) | > + _calc_vm_trans(flags, MAP_UNINITIALIZED, VM_UNINITIALIZED) | > _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ); > } > #endif /* __KERNEL__ */ > diff --git a/init/Kconfig b/init/Kconfig > index 43298f9..428e047 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1259,7 +1259,7 @@ endchoice > > config MMAP_ALLOW_UNINITIALIZED > bool "Allow mmapped anonymous memory to be uninitialized" > - depends on EXPERT && !MMU > + depends on EXPERT > default n > help > Normally, and according to the Linux spec, anonymous memory obtained > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index c3fdbcb..e6dd642 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1868,6 +1868,12 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma, > put_mems_allowed(); > return page; > } > + > +#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED > + if (!vma->vm_file && vma->vm_flags & VM_UNINITIALIZED) > + gfp &= ~__GFP_ZERO; > +#endif > + > /* > * fast path: default or task policy > */ Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href