shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-05 10:31:46 +09:00
Code Issues Packages Projects Releases Wiki Activity

xen: correctly check for pending events when restoring irq flags

Browse Source 
commit 7eb7ce4d2e 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.campbell@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
David Vrabel
2012-04-26 19:44:06 +01:00
committed by Greg Kroah-Hartman
parent d25895e8f1
commit aa4a6ac6d1
1 changed files with 1 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/xen/xen-asm.S
View File

@@ -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)