Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=c...
Commit: cd98a04a59e2f94fa64d5bf1e26498d27427d5e7
Parent: 45edb89ffd6386f95a7a9e1e5461b0e61c76aa14
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Wed Aug 13 18:02:18 2008 +0200
Committer: Linus Torvalds <torvalds@linux-foundation.org>
CommitDate: Fri Aug 15 11:45:19 2008 -0700
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>
---
include/asm-x86/mman.h | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/include/asm-x86/mman.h b/include/asm-x86/mman.h
index c1682b5..90bc410 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 */
--
...
