docs/110061: [PATCH] tuning(7) missing reference to vfs.read_max

[Alan Amesbury]

>Number:         110061
>Category:       docs
>Synopsis:       [PATCH] tuning(7) missing reference to vfs.read_max
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          update
>Submitter-Id:   current-users
>Arrival-Date:   Wed Mar 07 23:20:04 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Alan Amesbury
>Release:        6.1-RELEASE-p10
>Organization:
University of Minnesota
>Environment:
FreeBSD paulaner.oitsec.umn.edu 6.1-RELEASE-p10 FreeBSD 6.1-RELEASE-p10 #5: Tue Oct  3 13:31:01 CDT 2006     root at paulaner.oitsec.umn.edu:/usr/obj/usr/src/sys/OITSEC-6-IS  i386
>Description:
The tuning(7) manpage is missing documentation for vfs.read_max.  Since this knob can have a measurable, sometimes drastic, improvement on read performance for some systems, I think it deserves some mention.
>How-To-Repeat:
Read tuning(7) and note absence of mention of vfs.read_max.
>Fix:
This patch, derived against

$FreeBSD: src/share/man/man7/tuning.7,v 1.72 2005/06/30 13:04:25 hmp Exp $


may work.

---------- Patch for tuning(7) ----------

--- tuning.7.ORIG       Wed Mar  7 16:37:36 2007
+++ tuning.7    Wed Mar  7 17:04:37 2007
@@ -464,6 +464,13 @@
 higher write queueing values may add latency to reads occurring at the same
 time.
 .Pp
+The
+.Va vfs.read_max
+sysctl (default 8) determines how many blocks to read ahead during sequential
+reads.  For system loads where lots of sequential reading is done,
+increasing this to 16 or 32 may increase performance, particularly for
+RAID systems.
+.Pp
 There are various other buffer-cache and VM page cache related sysctls.
 We do not recommend modifying these values.
 As of

-------- End patch for tuning(7) --------

I wasn't able to attach the patch using the webform's "And/or patch file" option, as it didn't seem to think it was a patch.
>Release-Note:
>Audit-Trail:
>Unformatted: