2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------
From: David Vrabel <david.vra...@citrix.com>
commit 7eb7ce4d2e8991aff4ecb71a81949a907ca755ac upstream.
In xen_restore_fl_direct(), xen_force_evtchn_callback() was being
called even if no events were pending. This resulted in (depending on
workload) about a 100 times as many xen_version hypercalls as
necessary.
Fix this by correcting the sense of the conditional jump.
This seems to give a significant performance benefit for some
workloads.
There is some subtle tricksy "..since the check here is trying to
check both pending and masked in a single cmpw, but I think this is
correct. It will call check_events now only when the combined
mask+pending word is 0x0001 (aka unmasked, pending)." (Ian)
Acked-by: Ian Campbell <ian.campb...@citrix.com>
Signed-off-by: David Vrabel <david.vra...@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w...@1wt.eu>
---
arch/x86/xen/xen-asm.S | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 79d7362..3e45aa0 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -96,7 +96,7 @@ ENTRY(xen_restore_fl_direct)
/* check for unmasked and pending */
cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
- jz 1f
+ jnz 1f
2: call check_events
1:
ENDPATCH(xen_restore_fl_direct)
--
1.7.2.1.45.g54fbc
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