x86, UV: Disable BAU on network congestion

The numalink network can become so congested that TLB shootdown
using the Broadcast Assist Unit becomes slower than using IPI's.

In that case, disable the use of the BAU for a period of time.
The period is tunable.  When the period expires the use of the
BAU is re-enabled. A count of these actions is added to the
statistics file.

Signed-off-by: Cliff Wickman <cpw@sgi.com>
Cc: gregkh@suse.de
LKML-Reference: <E1OJvNy-0004a4-0a@eag09.americas.sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/include/asm/uv/uv_bau.h b/arch/x86/include/asm/uv/uv_bau.h
index e5543c1a80ca..9b3e750ef2d8 100644
--- a/arch/x86/include/asm/uv/uv_bau.h
+++ b/arch/x86/include/asm/uv/uv_bau.h
@@ -34,6 +34,7 @@
  */
 
 #define UV_ITEMS_PER_DESCRIPTOR         8
+/* the 'throttle' to prevent the hardware stay-busy bug */
 #define MAX_BAU_CONCURRENT              3
 #define UV_CPUS_PER_ACT_STATUS          32
 #define UV_ACT_STATUS_MASK              0x3
@@ -338,6 +339,7 @@ struct bau_control {
         int timeout_tries;
         int ipi_attempts;
         int conseccompletes;
+        int baudisabled;
         int set_bau_off;
         short cpu;
         short uvhub_cpu;
@@ -389,6 +391,8 @@ struct ptc_stats {
         unsigned long s_busy; /* status stayed busy past s/w timer */
         unsigned long s_throttles; /* waits in throttle */
         unsigned long s_retry_messages; /* retry broadcasts */
+        unsigned long s_bau_reenabled; /* for bau enable/disable */
+        unsigned long s_bau_disabled; /* for bau enable/disable */
         /* destination statistics */
         unsigned long d_alltlb; /* times all tlb's on this cpu were flushed */
         unsigned long d_onetlb; /* times just one tlb on this cpu was flushed */