svn commit: r197801 - in projects/tcp_ffcaia2008_8.x/sys: kern sys

[Lawrence Stewart]

Author: lstewart
Date: Tue Oct  6 07:24:23 2009
New Revision: 197801
URL: http://svn.freebsd.org/changeset/base/197801

Log:
  Cannibalise an unused field in the ALE to store a count of the bytes written to
  the ALE by the consumer. This extends the alq_get/alq_post interface to allow a
  consumer to request an allocation from the ALQ that may be larger than is
  actually needed. Nothing changes in the default use case. The new use case made
  possible by this change is as follows:
   - Consumer requests X bytes from the ALQ using alq_getn().
   - Consumer only generates Y bytes of data (where Y < X) and writes them to
     the ALQ buffer location pointed to by ale->ae_data.
   - [New step] Consumer overwrites ale->ae_bytesused with the value of Y to
     inform alq_post() of the actual number of bytes written.
   - Consumer calls alq_post() to complete the write.
  
  Sponsored by:	FreeBSD Foundation

Modified:
  projects/tcp_ffcaia2008_8.x/sys/kern/kern_alq.c
  projects/tcp_ffcaia2008_8.x/sys/sys/alq.h

Modified: projects/tcp_ffcaia2008_8.x/sys/kern/kern_alq.c
==============================================================================
--- projects/tcp_ffcaia2008_8.x/sys/kern/kern_alq.c	Tue Oct  6 06:35:52 2009	(r197800)
+++ projects/tcp_ffcaia2008_8.x/sys/kern/kern_alq.c	Tue Oct  6 07:24:23 2009	(r197801)
@@ -668,15 +668,7 @@ alq_getn(struct alq *alq, int len, int f
 	 * available in our buffer starting at aq_writehead.
 	 */
 	alq->aq_getpost.ae_data = alq->aq_entbuf + alq->aq_writehead;
-	alq->aq_writehead += len;
-	alq->aq_freebytes -= len;
-
-	/* Wrap aq_writehead if we've filled to the end of the buffer. */
-	if (alq->aq_writehead == alq->aq_buflen)
-		alq->aq_writehead = 0;
-
-	KASSERT((alq->aq_writehead >= 0 && alq->aq_writehead < alq->aq_buflen),
-	    ("%s: aq_writehead < 0 || aq_writehead >= aq_buflen", __func__));
+	alq->aq_getpost.ae_bytesused = len;
 
 	return (&alq->aq_getpost);
 }
@@ -693,6 +685,16 @@ alq_post(struct alq *alq, struct ale *al
 	} else
 		activate = 0;
 
+	alq->aq_writehead += ale->ae_bytesused;
+	alq->aq_freebytes -= ale->ae_bytesused;
+
+	/* Wrap aq_writehead if we've filled to the end of the buffer. */
+	if (alq->aq_writehead == alq->aq_buflen)
+		alq->aq_writehead = 0;
+
+	KASSERT((alq->aq_writehead >= 0 && alq->aq_writehead < alq->aq_buflen),
+	    ("%s: aq_writehead < 0 || aq_writehead >= aq_buflen", __func__));
+
 	ALQ_UNLOCK(alq);
 
 	if (activate) {

Modified: projects/tcp_ffcaia2008_8.x/sys/sys/alq.h
==============================================================================
--- projects/tcp_ffcaia2008_8.x/sys/sys/alq.h	Tue Oct  6 06:35:52 2009	(r197800)
+++ projects/tcp_ffcaia2008_8.x/sys/sys/alq.h	Tue Oct  6 07:24:23 2009	(r197801)
@@ -42,7 +42,7 @@ extern struct thread *ald_thread;
  * Async. Logging Entry
  */
 struct ale {
-	struct ale	*ae_next;	/* Unused, compat. */
+	intptr_t	ae_bytesused;	/* # bytes written to ALE. */
 	char		*ae_data;	/* Write ptr. */
 	int		ae_flags;	/* Unused, compat. */
 };