>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@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:
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