From a57ac8ec23ba4df071c090a1d61707a997b1727c Mon Sep 17 00:00:00 2001
From: dimitr <dimitr@users.sourceforge.net>
Date: Tue, 27 Mar 2012 07:11:34 +0000
Subject: [PATCH] Optimized the shared counter generator to avoid LM calls if
 there's no contention on the protecting lock.

---
 src/jrd/Database.cpp | 8 +++++++-
 src/jrd/Database.h   | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/jrd/Database.cpp b/src/jrd/Database.cpp
index 99631b3ace..2ca189d26b 100644
--- a/src/jrd/Database.cpp
+++ b/src/jrd/Database.cpp
@@ -155,13 +155,18 @@ namespace Jrd
 			lock->lck_object = counter;
 			LCK_lock(tdbb, lock, LCK_PW, LCK_WAIT);
 
+			counter->isProtected = true;
 			counter->curVal = 1;
 			counter->maxVal = 0;
 		}
 
 		if (counter->curVal > counter->maxVal)
 		{
-			LCK_convert(tdbb, counter->lock, LCK_PW, LCK_WAIT);
+			if (!counter->isProtected)
+			{
+				LCK_convert(tdbb, counter->lock, LCK_PW, LCK_WAIT);
+				counter->isProtected = true;
+			}
 
 			counter->curVal = LCK_read_data(tdbb, counter->lock);
 
@@ -196,6 +201,7 @@ namespace Jrd
 			Jrd::ContextPoolHolder context(tdbb, dbb->dbb_permanent);
 
 			LCK_downgrade(tdbb, counter->lock);
+			counter->isProtected = false;
 		}
 		catch (const Firebird::Exception&)
 		{} // no-op
diff --git a/src/jrd/Database.h b/src/jrd/Database.h
index b35e72703b..cfefbe6a31 100644
--- a/src/jrd/Database.h
+++ b/src/jrd/Database.h
@@ -287,6 +287,7 @@ public:
 		struct ValueCache
 		{
 			Lock* lock;
+			bool isProtected;
 			SLONG curVal;
 			SLONG maxVal;
 		};