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authorAlexander Graf <agraf@suse.de>2013-11-25 22:46:55 +0100
committerAnthony Liguori <aliguori@amazon.com>2013-11-25 20:35:12 -0800
commit84dc96e1e51c74ebf40b6c5e0c383769402e1a2d (patch)
tree217240d94792a76402aac310c20645c984315358
parent455df3f32341a3dff00f1726ff0749b3dd783bdf (diff)
PPC: BookE: Make FIT/WDT timers at best millisecond grained
The default granularity for the FIT timer on 440 is on every 0x1000th transition of TB from 0 to 1. Translated that means 48828 times a second. Since interrupts are quite expensive for 440 and we don't really care about the accuracy of the FIT to that significance, let's force FIT and WDT to at best millisecond granularity. This basically restores behavior as it was in QEMU 1.6, where timers could only deal with millisecond granularities at all. This patch greatly improves performance with the 440 target and restores roughly the same performance level that QEMU 1.6 had for me. Signed-off-by: Alexander Graf <agraf@suse.de> Message-id: 1385416015-22775-3-git-send-email-agraf@suse.de Signed-off-by: Anthony Liguori <aliguori@amazon.com>
-rw-r--r--hw/ppc/ppc_booke.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/hw/ppc/ppc_booke.c b/hw/ppc/ppc_booke.c
index 56c4196735..b421620708 100644
--- a/hw/ppc/ppc_booke.c
+++ b/hw/ppc/ppc_booke.c
@@ -174,6 +174,12 @@ static void booke_update_fixed_timer(CPUPPCState *env,
if (*next == now) {
(*next)++;
+ } else {
+ /*
+ * There's no point to fake any granularity that's more fine grained
+ * than milliseconds. Anything beyond that just overloads the system.
+ */
+ *next = MAX(*next, now + SCALE_MS);
}
/* Fire the next timer */