blk-cgroup: Initialize ioc->cgroup_changed at ioc creation time

PATCH In review Vivek Goyal 2 participants 2 messages May 23, 2011 Block layer

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Vivek Goyal

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2011-05-23 14:55 UTC #0 lore raw

PATCH 1/1 blk-cgroup: Initialize ioc->cgroup_changed at ioc creation time

If we don't explicitly initialize it to zero, CFQ might think that cgroup of ioc has changed and it generates lots of unnecessary calls to call_for_each_cic(changed_cgroup). Fix it.

cfq_get_io_context()
cfq_ioc_set_cgroup()
call_for_each_cic(ioc, changed_cgroup)

Signed-off-by Vivek Goyal <[email protected]>

---
 block/blk-ioc.c |    3 +++
 1 file changed, 3 insertions(+)

block/blk-ioc.c +3 -0

Index: linux-2.6-block/block/blk-ioc.c
===================================================================
@@ -96,6 +96,9 @@ struct io_context *alloc_io_context(gfp_
 		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
 		INIT_HLIST_HEAD(&ret->cic_list);
 		ret->ioc_data = NULL;
+#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
+		ret->cgroup_changed = 0;
+#endif
 	}
 
 	return ret;

Jens Axboe

2011-05-23 17:36 UTC #1 lore raw

Quoted 7 lines · Vivek Goyal

If we don't explicitly initialize it to zero, CFQ might think that cgroup of ioc has changed and it generates lots of unnecessary calls to call_for_each_cic(changed_cgroup). Fix it.
cfq_get_io_context()
cfq_ioc_set_cgroup()
call_for_each_cic(ioc, changed_cgroup)

Thanks Vivek, applied.

Signature · 1 line

Jens Axboe