NetBSD Problem Report #28374

From www@netbsd.org  Sun Nov 21 08:31:57 2004
Return-Path: <www@netbsd.org>
Received: by narn.netbsd.org (Postfix, from userid 31301)
	id 51D042525D0; Sun, 21 Nov 2004 08:31:57 +0000 (UTC)
Message-Id: <20041121083157.51D042525D0@narn.netbsd.org>
Date: Sun, 21 Nov 2004 08:31:57 +0000 (UTC)
From: arto@selonen.org
Reply-To: arto@selonen.org
To: gnats-bugs@netbsd.org
Subject: vmstat(1) reports more pages freed by page daemon than actually are
X-Send-Pr-Version: www-1.0

>Number:         28374
>Category:       bin
>Synopsis:       vmstat(1) reports more pages freed by page daemon than actually are
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Nov 21 08:32:00 +0000 2004
>Originator:     Arto Selonen
>Release:        NetBSD 2.99.10 from ~20041109 sources
>Organization:
>Environment:
NetBSD blah 2.99.10 NetBSD 2.99.10 (BLAH) #74: Tue Nov  9 10:35:31 EET 2004  blah@blah:/obj/sys/arch/i386/compile/BLAH i386
>Description:
Running 'vmstat -s' produces (among other things):
  1072242 pages freed by daemon
     5059 anonymous pages scanned by daemon
   706468 object pages scanned by daemon

Inspecting code of uvmpd_scan_inactive() in sys/uvm/uvm_pdaemon.c
reveals that the number of pages freed by the *page daemon*
can not be larger than the above anonymous+object pages scanned.

The discrepancy is caused by uvmexp.pdfreed (documented as
'/* number of pages daemon freed since boot */' in
/usr/src/sys/uvm/uvm_extern.h) being incremented by others
than page daemon (or what daemon is it referring to?). A quick grep
reveals that at least the following files seem to contain code
that increments the counter:

/usr/src/sys/uvm/uvm_pager.c
/usr/src/sys/miscfs/genfs/genfs_vnops.c

>How-To-Repeat:
Code inspection:

/usr/src/sys/uvm/uvm_extern.h
/usr/src/usr.bin/vmstat/vmstat.c
/usr/src/sys/uvm/uvm_pdaemon.c
/usr/src/sys/uvm/uvm_pager.c

Run 'vmstat -s', observe that 'pages freed by daemon' is larger
than what page daemon could have freed.
>Fix:
Either change the description of the counter in both uvm_extern.h and
vmstat.c (to eg. 'pages freed'), or use two counters (one for page daemon, one for others). Or describe which daemon is in question, if not page
daemon.

Home	PR Database Search