Re: no pv entries: increase vm.pmap.shpgperproc
- From: Bill Moran <wmoran@xxxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 22 Jan 2007 09:12:18 -0500
In response to "peter" <peter@xxxxxxxxxxxxxxxxx>:
In response to "peter" <peter@xxxxxxxxxxxxxxxxx>:
Hi,
My freebsd box runs the apache httpd2.0 server, postgresql8.1server,
Recently, I got the below info in /var/crash.
“Dump header from device /dev/da0s1b
Architecture: i386
Architecture Version: 2
Dump Length: 1073127424B (1023 MB)
Blocksize: 512
Dumptime: Wed Jan 17 16:39:08 2007
Hostname: myhost.mydomain.com
Magic: FreeBSD Kernel Dump
Version String: FreeBSD 6.0-RELEASE #0: Tue Apr 25 15:07:33 CST 2006
peter@xxxxxxxxxxxxxxxxxxx:/usr/src/sys/i386/compile/MYKNL
Panic String: no pv entries: increase vm.pmap.shpgperproc
Dump Parity: 2383301964
Bounds: 49
Dump Status: good”
I had searched in google, but I didn’t know how to do.
You _should_ be able to raise the vm.pmap.shpgperproc sysctl to prevent
the problem -- but there doesn't seem to be any such sysctl. I'm not sure
what's going on here, but it seems to me that a PR is in order.
I had ever added the line "kern.vm.pmap.shpgperproc=4096" to /boot/loader.conf ,
but it seems to be ineffective.
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/108121
Failing that, you could set the following in your kernel config:
options PMAP_SHPGPERPROC=250
and rebuild/reinstall your kernel.
The default value is 200, so I expect 250 will be enough of a bump to
fix the problem. If it's not, raise it a little higher and try again.
I don't know of any way to tell exactly what this value should be other
than trial and error. I've seen warnings that raising this value too
high can result in an unbootable kernel, so take care to understand how
to recover from the installation of an unbootable kernel.
How to know the default value?
Experiment. You can also look at the PV line in the sysctl vm.zone, but
I'm not sure how to interpret that information.
The website on the box has about 22000 visits every day, so i think the
physical memory size maybe small.
OK.
I configured httpd.conf like this:
....
KeepAlive Off
....
<IfModule prefork.c>
StartServers 8
MinSpareServers 3
MaxSpareServers 5
ServerLimit 170
MaxClients 160
MaxRequestsPerChild 300
</IfModule>
.....
If this is a dedicated web server, you sure are configuring it wrong.
First off, you tell it to start 8 workers, then immediately kill off
three of them to meet the MaxSpareServers. That's pretty minor, however,
as it only happens at startup.
MaxSpareServers of 5 is pretty low for a busy webserver. If the site
is seeing a lot of traffic, or the traffic is erratic, you're forcing
Apache to try to constantly tune itself to exactly what the load is.
If this server is dedicated to webserving, you'd do better to raise
MaxSpareServers to something like 25, so you have some spare capacity
when the load spikes instead of forcing Apache to do a lot of forking,
then kill off a lot of processes, then fork a lot of them again ...
But that discussion belongs on the Apache lists ...
--
Bill Moran
Collaborative Fusion Inc.
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- From: peter
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- From: Bill Moran
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