svn commit: r251464 - stable/8/sys/geom

[Steven Hartland]

Author: smh
Date: Thu Jun  6 10:25:58 2013
New Revision: 251464
URL: http://svnweb.freebsd.org/changeset/base/251464

Log:
  MFC r249930:
  Added a sysctl to control the maximum size of a delete request

Modified:
  stable/8/sys/geom/geom_dev.c
Directory Properties:
  stable/8/sys/   (props changed)
  stable/8/sys/geom/   (props changed)

Modified: stable/8/sys/geom/geom_dev.c
==============================================================================
--- stable/8/sys/geom/geom_dev.c	Thu Jun  6 10:09:20 2013	(r251463)
+++ stable/8/sys/geom/geom_dev.c	Thu Jun  6 10:25:58 2013	(r251464)
@@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/disk.h>
 #include <sys/fcntl.h>
 #include <sys/limits.h>
+#include <sys/sysctl.h>
 #include <geom/geom.h>
 #include <geom/geom_int.h>
 
@@ -80,6 +81,19 @@ static struct g_class g_dev_class	= {
 	.orphan = g_dev_orphan,
 };
 
+/*
+ * We target 262144 (8 x 32768) sectors by default as this significantly
+ * increases the throughput on commonly used SSD's with a marginal
+ * increase in non-interruptible request latency.
+ */
+static uint64_t g_dev_del_max_sectors = 262144;
+SYSCTL_DECL(_kern_geom);
+SYSCTL_NODE(_kern_geom, OID_AUTO, dev, CTLFLAG_RW, 0, "GEOM_DEV stuff");
+SYSCTL_QUAD(_kern_geom_dev, OID_AUTO, delete_max_sectors, CTLFLAG_RW,
+    &g_dev_del_max_sectors, 0, "Maximum number of sectors in a single "
+    "delete request sent to the provider. Larger requests are chunked "
+    "so they can be interrupted. (0 = disable chunking)");
+
 void
 g_dev_print(void)
 {
@@ -326,17 +340,20 @@ g_dev_ioctl(struct cdev *dev, u_long cmd
 		}
 		while (length > 0) { 
 			chunk = length;
-			if (chunk > 65536 * cp->provider->sectorsize)
-				chunk = 65536 * cp->provider->sectorsize;
+			if (g_dev_del_max_sectors != 0 && chunk >
+			    g_dev_del_max_sectors * cp->provider->sectorsize) {
+				chunk = g_dev_del_max_sectors *
+				    cp->provider->sectorsize;
+			}
 			error = g_delete_data(cp, offset, chunk);
 			length -= chunk;
 			offset += chunk;
 			if (error)
 				break;
 			/*
-			 * Since the request size is unbounded, the service
-			 * time is likewise.  We make this ioctl interruptible
-			 * by checking for signals for each bio.
+			 * Since the request size can be large, the service
+			 * time can be is likewise.  We make this ioctl
+			 * interruptible by checking for signals for each bio.
 			 */
 			if (SIGPENDING(td))
 				break;