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authorChen, Kenneth W <kenneth.w.chen@intel.com>2005-09-09 13:02:02 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-09 13:57:31 -0700
commit383f2835eb9afb723af71850037b2f074ac9db60 (patch)
tree1ef99fd4d7246b2afa16dc7d1514b6ff25fa8284 /include
parentb0d62e6d5b3318b6b722121d945afa295f7201b5 (diff)
[PATCH] Prefetch kernel stacks to speed up context switch
For architecture like ia64, the switch stack structure is fairly large (currently 528 bytes). For context switch intensive application, we found that significant amount of cache misses occurs in switch_to() function. The following patch adds a hook in the schedule() function to prefetch switch stack structure as soon as 'next' task is determined. This allows maximum overlap in prefetch cache lines for that structure. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "Luck, Tony" <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include')
-rw-r--r--include/asm-ia64/system.h1
-rw-r--r--include/linux/sched.h5
2 files changed, 6 insertions, 0 deletions
diff --git a/include/asm-ia64/system.h b/include/asm-ia64/system.h
index 33256db4a7c..635235fa1e3 100644
--- a/include/asm-ia64/system.h
+++ b/include/asm-ia64/system.h
@@ -275,6 +275,7 @@ extern void ia64_load_extra (struct task_struct *task);
*/
#define __ARCH_WANT_UNLOCKED_CTXSW
+#define ARCH_HAS_PREFETCH_SWITCH_STACK
#define ia64_platform_is(x) (strcmp(x, platform_name) == 0)
void cpu_idle_wait(void);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ea1b5f32ec5..c551e6a1447 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -604,6 +604,11 @@ extern int groups_search(struct group_info *group_info, gid_t grp);
#define GROUP_AT(gi, i) \
((gi)->blocks[(i)/NGROUPS_PER_BLOCK][(i)%NGROUPS_PER_BLOCK])
+#ifdef ARCH_HAS_PREFETCH_SWITCH_STACK
+extern void prefetch_stack(struct task_struct*);
+#else
+static inline void prefetch_stack(struct task_struct *t) { }
+#endif
struct audit_context; /* See audit.c */
struct mempolicy;