Date: Sun, 7 Sep 2008 00:04:48 +0200 From: Laurent Frigault <lfrigault@agneau.org> To: freebsd-stable@freebsd.org, freebsd-hackers@FreeBSD.org Subject: how to compute vm.pmap.pv_entry_count from procstat ? Message-ID: <20080906220448.GA78044@obelix.bergerie.agneau.org>
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Hi, On a 7.0-STABLE i386 web server, I got kernel messages reporting problems with PV entries: Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable. This server (DELL poweredge R200 quad core 4G RAM) is having random hang every few weeks (need power off/on cycle, IPMI not responding any more with those hangs) , but I don't know if the hangs are related to a PV entries problem. Before increasing blindly vm.pmap.shpgperproc , I would like to evaluate a good value for vm.pmap.shpgperproc (default 200) because I remember reading somewhere that increasing too much shpgperproc could result in panic at boot time or later. If I guess correctly (I did not find any understandable by me documentation on vm.pmap.*) vm.pmap.pv_entry_count is the value of currently used PV entries . My idea was to use procstat -av output to compute some statistics about the number of PV entries needed by various kind of process (apache, ...) It should be possible to compute a good evaluation of vm.pmap.pv_entry_count by adding some combination of RES,PRES, SHD columns. When I add RES,PRES, SHD values, the result is bigger than pv_entry_count. What is the formula to retrieve pv_entry_count from procstat output or in other words, how to compute the number of PV entries used by a process ? Regards, -- Laurent Frigault | <url:http://www.agneau.org/>;
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