X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=blobdiff_plain;f=module%2Fzfs%2Fvdev_disk.c;h=aba3c4ab57ef284df3641bb3661312eef8cb2419;hb=777d4af89137907adc91377327505f40c296035d;hp=3e59bd22615efbb417f2f8e02a2ba7844526f7fe;hpb=e06be586410cdad14d2dce76af4f2d43eebe7c83;p=zfs.git

diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index 3e59bd2..aba3c4a 100644
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -33,6 +33,8 @@
 #include <sys/zio.h>
 #include <sys/sunldi.h>
 
+char *zfs_vdev_scheduler = VDEV_SCHEDULER;
+
 /*
  * Virtual device vector for disks.
  */
@@ -102,6 +104,43 @@ vdev_disk_error(zio_t *zio)
 #endif
 }
 
+/*
+ * Use the Linux 'noop' elevator for zfs managed block devices.  This
+ * strikes the ideal balance by allowing the zfs elevator to do all
+ * request ordering and prioritization.  While allowing the Linux
+ * elevator to do the maximum front/back merging allowed by the
+ * physical device.  This yields the largest possible requests for
+ * the device with the lowest total overhead.
+ *
+ * Unfortunately we cannot directly call the elevator_switch() function
+ * because it is not exported from the block layer.  This means we have
+ * to use the sysfs interface and a user space upcall.  Pools will be
+ * automatically imported on module load so we must do this at device
+ * open time from the kernel.
+ */
+static int
+vdev_elevator_switch(vdev_t *v, char *elevator, char *device)
+{
+	char sh_path[] = "/bin/sh";
+	char sh_cmd[128];
+	char *argv[] = { sh_path, "-c", sh_cmd };
+	char *envp[] = { NULL };
+	int error;
+
+	if (!strncmp(elevator, "none", 4) && (strlen(elevator) == 4))
+		return (0);
+
+	sprintf(sh_cmd, "%s \"%s\" >/sys/block/%s/queue/scheduler",
+	    "/bin/echo", elevator, device);
+
+	error = call_usermodehelper(sh_path, argv, envp, 1);
+	if (error)
+		printk("ZFS: Unable to set \"%s\" scheduler for %s (%s): %d\n",
+		    elevator, v->vdev_path, device, error);
+
+	return (error);
+}
+
 static int
 vdev_disk_open(vdev_t *v, uint64_t *psize, uint64_t *ashift)
 {
@@ -167,6 +206,10 @@ vdev_disk_open(vdev_t *v, uint64_t *psize, uint64_t *ashift)
 	/* Based on the minimum sector size set the block size */
 	*ashift = highbit(MAX(block_size, SPA_MINBLOCKSIZE)) - 1;
 
+	/* Try to set the io scheduler elevator algorithm */
+	(void) vdev_elevator_switch(v, zfs_vdev_scheduler,
+	    bdev->bd_disk->disk_name);
+
 	return 0;
 }
 
@@ -702,3 +745,6 @@ vdev_disk_read_rootlabel(char *devpath, char *devid, nvlist_t **config)
 
 	return 0;
 }
+
+module_param(zfs_vdev_scheduler, charp, 0644);
+MODULE_PARM_DESC(zfs_vdev_scheduler, "IO Scheduler (noop)");