[win-pv-devel] [PATCH] Kick notifier DPC directly.

[Owen Smith <owen.smith@xxxxxxxxxx>]

EVTCHN(Trigger, ...) was changed with the FiFo event channel
implementation, which led to a performance regression. Kicking
the notifier does not require triggering the local end of the
event channel, so shortcut this process by queueing the notifier
DPC directly.

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/xenvbd/notifier.c | 12 ++++++++++++
 src/xenvbd/notifier.h |  5 +++++
 src/xenvbd/pdo.c      |  8 ++++----
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/xenvbd/notifier.c b/src/xenvbd/notifier.c
index b812d69..e9943fa 100644
--- a/src/xenvbd/notifier.c
+++ b/src/xenvbd/notifier.c
@@ -312,6 +312,18 @@ NotifierDebugCallback(
 }
 
 VOID
+NotifierKick(
+    IN  PXENVBD_NOTIFIER            Notifier
+    )
+{
+    if (Notifier->Enabled) {
+               if (KeInsertQueueDpc(&Notifier->Dpc, NULL, NULL)) {
+                       ++Notifier->NumDpcs;
+        }
+    }
+}
+
+VOID
 NotifierTrigger(
     IN  PXENVBD_NOTIFIER            Notifier
     )
diff --git a/src/xenvbd/notifier.h b/src/xenvbd/notifier.h
index 1c368e6..4cf35e7 100644
--- a/src/xenvbd/notifier.h
+++ b/src/xenvbd/notifier.h
@@ -84,6 +84,11 @@ NotifierDebugCallback(
     );
 
 extern VOID
+NotifierKick(
+    IN  PXENVBD_NOTIFIER            Notifier
+    );
+
+extern VOID
 NotifierTrigger(
     IN  PXENVBD_NOTIFIER            Notifier
     );
diff --git a/src/xenvbd/pdo.c b/src/xenvbd/pdo.c
index e00729e..198c4d3 100644
--- a/src/xenvbd/pdo.c
+++ b/src/xenvbd/pdo.c
@@ -1860,7 +1860,7 @@ PdoReadWrite(
     }
 
     QueueAppend(&Pdo->FreshSrbs, &SrbExt->Entry);
-    NotifierTrigger(Notifier);
+    NotifierKick(Notifier);
 
     return FALSE;
 }
@@ -1889,7 +1889,7 @@ PdoSyncCache(
     }
 
     QueueAppend(&Pdo->FreshSrbs, &SrbExt->Entry);
-    NotifierTrigger(Notifier);
+    NotifierKick(Notifier);
 
     return FALSE;
 }
@@ -1918,7 +1918,7 @@ PdoUnmap(
     }
 
     QueueAppend(&Pdo->FreshSrbs, &SrbExt->Entry);
-    NotifierTrigger(Notifier);
+    NotifierKick(Notifier);
 
     return FALSE;
 }
@@ -2252,7 +2252,7 @@ __PdoQueueShutdown(
     PXENVBD_NOTIFIER    Notifier = FrontendGetNotifier(Pdo->Frontend);
 
     QueueAppend(&Pdo->ShutdownSrbs, &SrbExt->Entry);
-    NotifierTrigger(Notifier);
+    NotifierKick(Notifier);
 }
 
 static FORCEINLINE VOID
-- 
1.9.4.msysgit.1


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