From: Martin Hicks <mort@wildopensource.com>
Another optimization patch from Jack Steiner, intended to reduce TLB
flushes during process migration.
Most architextures should define tlb_migrate_prepare() to be flush_tlb_mm(),
but on i386, it would be a wasted flush, because i386 disconnects previous
cpus from the tlb flush automatically.
---
25-akpm/include/asm-generic/tlb.h | 2 ++
25-akpm/include/asm-ia64/tlb.h | 2 ++
25-akpm/kernel/sched.c | 9 +++++++++
3 files changed, 13 insertions(+)
diff -puN include/asm-generic/tlb.h~process-migration-speedup include/asm-generic/tlb.h
--- 25/include/asm-generic/tlb.h~process-migration-speedup 2004-03-25 11:13:02.836539968 -0800
+++ 25-akpm/include/asm-generic/tlb.h 2004-03-25 11:13:02.841539208 -0800
@@ -146,4 +146,6 @@ static inline void tlb_remove_page(struc
__pmd_free_tlb(tlb, pmdp); \
} while (0)
+#define tlb_migrate_prepare(mm) do { } while(0)
+
#endif /* _ASM_GENERIC__TLB_H */
diff -puN include/asm-ia64/tlb.h~process-migration-speedup include/asm-ia64/tlb.h
--- 25/include/asm-ia64/tlb.h~process-migration-speedup 2004-03-25 11:13:02.837539816 -0800
+++ 25-akpm/include/asm-ia64/tlb.h 2004-03-25 11:13:02.841539208 -0800
@@ -211,6 +211,8 @@ __tlb_remove_tlb_entry (struct mmu_gathe
tlb->end_addr = address + PAGE_SIZE;
}
+#define tlb_migrate_prepare(mm) flush_tlb_mm(mm)
+
#define tlb_start_vma(tlb, vma) do { } while (0)
#define tlb_end_vma(tlb, vma) do { } while (0)
diff -puN kernel/sched.c~process-migration-speedup kernel/sched.c
--- 25/kernel/sched.c~process-migration-speedup 2004-03-25 11:13:02.839539512 -0800
+++ 25-akpm/kernel/sched.c 2004-03-25 11:13:02.843538904 -0800
@@ -25,6 +25,7 @@
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
+#include <asm/tlb.h>
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
@@ -1119,6 +1120,14 @@ static void sched_migrate_task(task_t *p
task_rq_unlock(rq, &flags);
wake_up_process(rq->migration_thread);
wait_for_completion(&req.done);
+
+ /*
+ * we want a new context here. This eliminates TLB
+ * flushes on the cpus where the process executed prior to
+ * the migration.
+ */
+ tlb_migrate_prepare(current->mm);
+
return;
}
out:
_