kern/140091: [PATCH] allow for da(4) large block transfer than DFLTPHYS

[Artemiev Igor]

>Number:         140091
>Category:       kern
>Synopsis:       [PATCH] allow for da(4) large block transfer than DFLTPHYS
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Oct 29 20:50:01 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Artemiev Igor
>Release:        FreeBSD 7.2-STABLE i386
>Organization:
KlikSys
>Environment:
System: FreeBSD one.kliksys.ru 7.2-STABLE FreeBSD 7.2-STABLE #7: Sun May 17 14:54:10 MSD 2009 root at one.kliksys.ru:/usr/obj/usr/src.7/sys/KERNEL i386

>Description:
    By default, one transfer of data block limiting to DFLTPHYS for da(4), but modern controllers allow operate up to 128K per one DMA transaction, i.e. 3ware devices. This patch via loader.conf tunable allow scale d_maxsize by multiple DFLTPHYS.	
>How-To-Repeat:
    On my typical load (~4K active connections)

    Before:
    #iostat -dt da
                 da0
      KB/t tps  MB/s
    61.38 1731 56.31

# netstat -I igb0 -hw1
            input         (igb0)           output
   packets  errs      bytes    packets  errs      bytes colls
       41K     0        10M        30K     0        68M     0
       41K     0        11M        31K     0        68M     0
       42K     0        11M        31K     0        68M     0
       42K     0        11M        31K     0        68M     0
       42K     0       9.2M        31K     0        68M     0
       42K     0       9.8M        30K     0        59M     0
       42K     0        11M        30K     0        60M     0
       42K     0        11M        31K     0        68M     0
       42K     0        11M        31K     0        68M     0

    After:
#iostat -dt da
                 da0
      KB/t tps  MB/s
    127.29 827 80.18

# netstat -I igb0 -hw1
            input         (igb0)           output
   packets  errs      bytes    packets  errs      bytes colls
       46K     0        16M        69K     0        95M     0
       47K     0        18M        70K     0        95M     0
       48K     0        18M        71K     0        97M     0
       44K     0        13M        70K     0        98M     0
       40K     0       9.2M        68K     0        95M     0
       50K     0        21M        74K     0       100M     0
       49K     0        21M        71K     0        97M     0
       46K     0        16M        72K     0        99M     0
       51K     0        22M        75K     0       101M     0

>Fix:
    Apply this patch and reboot with kern.cam.da.max_size="2" in loader.conf

--- sys/cam/scsi/scsi_da.c.orig	2009-10-28 14:53:43.000000000 +0100
+++ sys/cam/scsi/scsi_da.c	2009-10-28 15:16:26.000000000 +0100
@@ -515,12 +515,16 @@
 static int da_retry_count = DA_DEFAULT_RETRY;
 static int da_default_timeout = DA_DEFAULT_TIMEOUT;
 static int da_send_ordered = DA_DEFAULT_SEND_ORDERED;
+static int da_max_size = 1;
 
 SYSCTL_NODE(_kern_cam, OID_AUTO, da, CTLFLAG_RD, 0,
             "CAM Direct Access Disk driver");
 SYSCTL_INT(_kern_cam_da, OID_AUTO, retry_count, CTLFLAG_RW,
            &da_retry_count, 0, "Normal I/O retry count");
 TUNABLE_INT("kern.cam.da.retry_count", &da_retry_count);
+TUNABLE_INT("kern.cam.da.max_size", &da_max_size);
+SYSCTL_INT(_kern_cam_da, OID_AUTO, max_size, CTLFLAG_RD,
+           &da_max_size, 0, "DFLTPHYS scale");
 SYSCTL_INT(_kern_cam_da, OID_AUTO, default_timeout, CTLFLAG_RW,
            &da_default_timeout, 0, "Normal I/O timeout (in seconds)");
 TUNABLE_INT("kern.cam.da.default_timeout", &da_default_timeout);
@@ -1201,7 +1205,10 @@
 	softc->disk->d_dump = dadump;
 	softc->disk->d_name = "da";
 	softc->disk->d_drv1 = periph;
-	softc->disk->d_maxsize = DFLTPHYS; /* XXX: probably not arbitrary */
+
+	if(da_max_size > 2)
+	    da_max_size = 1;
+	softc->disk->d_maxsize = da_max_size*DFLTPHYS; /* XXX: probably not arbitrary */
 	softc->disk->d_unit = periph->unit_number;
 	softc->disk->d_flags = DISKFLAG_NEEDSGIANT;
 	disk_create(softc->disk, DISK_VERSION);

>Release-Note:
>Audit-Trail:
>Unformatted: