From: Ingo Molnar <mingo@elte.hu>
The attached patch does a lock-break in copy_page_range() if needed, to
reduce scheduling latencies.
Has been tested as part of the -VP patchset.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/mm/memory.c | 19 +++++++++++++++++++
1 files changed, 19 insertions(+)
diff -puN mm/memory.c~sched-mm-fix-scheduling-latencies-in-copy_page_range mm/memory.c
--- 25/mm/memory.c~sched-mm-fix-scheduling-latencies-in-copy_page_range Tue Sep 14 17:39:57 2004
+++ 25-akpm/mm/memory.c Tue Sep 14 17:39:57 2004
@@ -337,6 +337,25 @@ cont_copy_pte_range_noset:
}
src_pte++;
dst_pte++;
+ /*
+ * We are holding two locks at this point -
+ * any of them could generate latencies in
+ * another task on another CPU:
+ */
+ if (need_resched() ||
+ need_lockbreak(&src->page_table_lock) ||
+ need_lockbreak(&dst->page_table_lock))
+ {
+ pte_unmap_nested(src_pte);
+ pte_unmap(dst_pte);
+ spin_unlock(&src->page_table_lock);
+ spin_unlock(&dst->page_table_lock);
+ cond_resched();
+ spin_lock(&dst->page_table_lock);
+ spin_lock(&src->page_table_lock);
+ dst_pte = pte_offset_map(dst_pmd, address);
+ src_pte = pte_offset_map_nested(src_pmd, address);
+ }
} while ((unsigned long)src_pte & PTE_TABLE_MASK);
pte_unmap_nested(src_pte-1);
pte_unmap(dst_pte-1);
_