[PATCH 19/28] Drivers: hv: Add code to distribute channel interrupt load

K. Y. Srinivasan
2012-12-01T14:25:53Z

Implement a simple policy for distributing incoming interrupt load.
We classify channels as (a) performance critical and (b) not
performance critical. All non-performance critical channels will
be bound to the boot cpu. Performance critical channels will be
bound to the remaining available CPUs on a round-robin basis.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
drivers/hv/channel_mgmt.c | 85 ++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 84 insertions(+), 1 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 56ed45c..c80fe62 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -257,6 +257,89 @@ static void vmbus_process_offer(struct work_struct *work)
}
}

+enum {
+ IDE = 0,
+ SCSI,
+ NIC,
+ MAX_PERF_CHN,
+};
+
+/*
+ * This is an array of channels (devices) that are performance critical.
+ * We attempt to distribute the interrupt load for these devices across
+ * all available CPUs.
+ */
+static const uuid_le hp_devs[] = {
+ /* {32412632-86cb-44a2-9b5c-50d1417354f5} */
+ /* IDE */
+ {
+ .b = {
+ 0x32, 0x26, 0x41, 0x32, 0xcb, 0x86, 0xa2, 0x44,
+ 0x9b, 0x5c, 0x50, 0xd1, 0x41, 0x73, 0x54, 0xf5
+ }
+ },
+ /* {ba6163d9-04a1-4d29-b605-72e2ffb1dc7f} */
+ /* Storage - SCSI */
+ {
+ .b = {
+ 0xd9, 0x63, 0x61, 0xba, 0xa1, 0x04, 0x29, 0x4d,
+ 0xb6, 0x05, 0x72, 0xe2, 0xff, 0xb1, 0xdc, 0x7f
+ }
+ },
+ /* {F8615163-DF3E-46c5-913F-F2D2F965ED0E} */
+ /* Network */
+ {
+ .b = {
+ 0x63, 0x51, 0x61, 0xF8, 0x3E, 0xDF, 0xc5, 0x46,
+ 0x91, 0x3F, 0xF2, 0xD2, 0xF9, 0x65, 0xED, 0x0E
+ }
+ },
+
+};
+
+
+/*
+ * We use this state to statically distribute the channel interrupt load.
+ */
+static u32 next_vp;
+
+/*
+ * Starting with Win8, we can statically distribute the incoming
+ * channel interrupt load by binding a channel to VCPU. We
+ * implement here a simple round robin scheme for distributing
+ * the interrupt load.
+ * We will bind channels that are not performance critical to cpu 0 and
+ * performance critical channels (IDE, SCSI and Network) will be uniformly
+ * distributed across all available CPUs.
+ */
+static u32 get_vp_index(uuid_le *type_guid)
+{
+ u32 cur_cpu;
+ int i;
+ bool perf_chn = false;
+ u32 max_cpus = num_online_cpus();
+
+ for (i = IDE; i < MAX_PERF_CHN; i++) {
+ if (!memcmp(type_guid->b, hp_devs[i].b,
+ sizeof(uuid_le))) {
+ perf_chn = true;
+ break;
+ }
+ }
+ if ((vmbus_proto_version == VERSION_WS2008) ||
+ (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
+ /*
+ * Prior to win8, all channel interrupts are
+ * delivered on cpu 0.
+ * Also if the channel is not a performance critical
+ * channel, bind it to cpu 0.
+ */
+ return 0;
+ }
+ cur_cpu = (++next_vp % max_cpus);
+ return hv_context.vp_index[cur_cpu];
+}
+
/*
* vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
*
@@ -302,7 +385,7 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
offer->connection_id;
}

- newchannel->target_vp = 0;
+ newchannel->target_vp = get_vp_index(&offer->offer.if_type);

memcpy(&newchannel->offermsg, offer,
sizeof(struct vmbus_channel_offer_channel));
--
1.7.4.1