From cd98a04a59e2f94fa64d5bf1e26498d27427d5e7 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 13 Aug 2008 18:02:18 +0200 Subject: [PATCH] x86: add MAP_STACK mmap flag as per this discussion: http://lkml.org/lkml/2008/8/12/423 Pardo reported that 64-bit threaded apps, if their stacks exceed the combined size of ~4GB, slow down drastically in pthread_create() - because glibc uses MAP_32BIT to allocate the stacks. The use of MAP_32BIT is a legacy hack - to speed up context switching on certain early model 64-bit P4 CPUs. So introduce a new flag to be used by glibc instead, to not constrain 64-bit apps like this. glibc can switch to this new flag straight away - it will be ignored by the kernel. If those old CPUs ever matter to anyone, support for it can be implemented. Signed-off-by: Ingo Molnar Acked-by: Ulrich Drepper Signed-off-by: Linus Torvalds --- include/asm-x86/mman.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/asm-x86/mman.h b/include/asm-x86/mman.h index c1682b542dafe..90bc4108a4fdf 100644 --- a/include/asm-x86/mman.h +++ b/include/asm-x86/mman.h @@ -12,6 +12,7 @@ #define MAP_NORESERVE 0x4000 /* don't check for reservations */ #define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */ #define MAP_NONBLOCK 0x10000 /* do not block on IO */ +#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */ #define MCL_CURRENT 1 /* lock all current mappings */ #define MCL_FUTURE 2 /* lock all future mappings */