From 0b8be48baf5750ba2cb723deb037de44bbf4c385 Mon Sep 17 00:00:00 2001
From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Wed, 29 May 2013 10:24:49 -0600
Subject: [PATCH] Made some of the Rock collapsing behavior dependent on
 collapsed_forwarding.

Do not write empty rock I/O buffer to disk.

Added more comments and polished.
---
 src/fs/rock/RockIoState.cc | 8 ++++++--
 src/fs/rock/RockIoState.h  | 2 +-
 src/fs/rock/RockSwapDir.cc | 6 ++++--
 src/ipc/Messages.h         | 3 ++-
 4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/fs/rock/RockIoState.cc b/src/fs/rock/RockIoState.cc
index f8e461eb83..c7ed4722c5 100644
--- a/src/fs/rock/RockIoState.cc
+++ b/src/fs/rock/RockIoState.cc
@@ -175,11 +175,14 @@ Rock::IoState::tryWrite(char const *buf, size_t size, off_t coreOff)
             const SlotId sidNext = reserveSlotForWriting(); // throws
             assert(sidNext >= 0);
             writeToDisk(sidNext);
+        } else if (Config.onoff.collapsed_forwarding) {
+            // write partial buffer for all collapsed hit readers to see
+            // XXX: can we check that this is needed w/o stalling readers
+            // that appear right after our check?
+            writeBufToDisk(false);
         }
     }
 
-    // XXX: check that there are workers waiting for data, i.e. readers > 0
-    writeBufToDisk();
 }
 
 /// Buffers incoming data for the current slot.
@@ -242,6 +245,7 @@ Rock::IoState::writeToDisk(const SlotId sidNext)
     sidCurrent = sidNext;
 }
 
+/// Write header-less (XXX) or complete buffer to disk.
 void
 Rock::IoState::writeBufToDisk(const bool last)
 {
diff --git a/src/fs/rock/RockIoState.h b/src/fs/rock/RockIoState.h
index ee6f6a3dfc..f22a736e0a 100644
--- a/src/fs/rock/RockIoState.h
+++ b/src/fs/rock/RockIoState.h
@@ -50,7 +50,7 @@ private:
     void tryWrite(char const *buf, size_t size, off_t offset);
     size_t writeToBuffer(char const *buf, size_t size);
     void writeToDisk(const SlotId nextSlot);
-    void writeBufToDisk(const bool last = false);
+    void writeBufToDisk(const bool last);
     SlotId reserveSlotForWriting();
     
     void callBack(int errflag);
diff --git a/src/fs/rock/RockSwapDir.cc b/src/fs/rock/RockSwapDir.cc
index 5b08b23839..a732232fd7 100644
--- a/src/fs/rock/RockSwapDir.cc
+++ b/src/fs/rock/RockSwapDir.cc
@@ -748,8 +748,10 @@ Rock::SwapDir::writeCompleted(int errflag, size_t rlen, RefCount< ::WriteRequest
         return;
     }
 
-    // XXX: check that there are workers waiting for data, i.e. readers > 0
-    CollapsedForwarding::NewData(sio);
+    // XXX: can we check that this is needed w/o stalling readers
+    // that appear right after our check?
+    if (Config.onoff.collapsed_forwarding)
+        CollapsedForwarding::NewData(sio);
 
     if (errflag == DISK_OK) {
         // do not increment sio.offset_ because we do it in sio->write()
diff --git a/src/ipc/Messages.h b/src/ipc/Messages.h
index 14837ff81b..e7e8d07f9b 100644
--- a/src/ipc/Messages.h
+++ b/src/ipc/Messages.h
@@ -15,7 +15,8 @@ namespace Ipc
 typedef enum { mtNone = 0, mtRegistration,
                mtStrandSearchRequest, mtStrandSearchResponse,
                mtSharedListenRequest, mtSharedListenResponse,
-               mtIpcIoNotification, mtCollapsedForwardingNotification,
+               mtIpcIoNotification,
+               mtCollapsedForwardingNotification,
                mtCacheMgrRequest, mtCacheMgrResponse
 #if SQUID_SNMP
                ,
-- 
2.39.5