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authorIngo Molnar <mingo@elte.hu>2008-08-13 18:02:18 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2008-08-15 11:45:19 -0700
commitcd98a04a59e2f94fa64d5bf1e26498d27427d5e7 (patch)
treea6e9c7996612e52eb4ac2dc0d03046120965efc1
parent45edb89ffd6386f95a7a9e1e5461b0e61c76aa14 (diff)
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 <mingo@elte.hu> Acked-by: Ulrich Drepper <drepper@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/asm-x86/mman.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/asm-x86/mman.h b/include/asm-x86/mman.h
index c1682b542da..90bc4108a4f 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 */