[Xen-devel] [PATCHv2 5/5] evtchn: pad struct evtchn to 64 bytes

[David Vrabel <david.vrabel@xxxxxxxxxx>]

The number of struct evtchn in a page must be a power of two.  Under
some workloads performance is improved slightly by padding struct
evtchn to 64 bytes (a cache line), thus putting the per-channel locks
into their own cache line.

This does not decrease the number of struct evtchn's per-page.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
I'm not sure we actually want to do this.  I think it would be better
to pack the struct evtchn and use vmap to turn the pages into a linear
array for quicker lookup.
---
 xen/include/xen/sched.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 44ea92d..a0ff9d2 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -129,7 +129,7 @@ struct evtchn
 #endif
     } ssid;
 #endif
-};
+} __attribute__((aligned(64)));
 
 int  evtchn_init(struct domain *d); /* from domain_create */
 void evtchn_destroy(struct domain *d); /* from domain_kill */
-- 
1.7.10.4


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