Date: Tue, 1 Sep 2009 22:16:30 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Per olof Ljungmark <peo@intersonic.se> Cc: freebsd-questions@freebsd.org Subject: Re: memory usage displsy Message-ID: <20090902031626.GD2855@dan.emsphone.com> In-Reply-To: <4A9DB3AE.1000400@intersonic.se> References: <4A9D8057.8020307@intersonic.se> <20090901162931.d85ec256.wmoran@potentialtech.com> <20090901204147.GC2855@dan.emsphone.com> <4A9DB3AE.1000400@intersonic.se>
next in thread | previous in thread | raw e-mail | index | archive | help
In the last episode (Sep 02), Per olof Ljungmark said: > Dan Nelson wrote: > > In the last episode (Sep 01), Bill Moran said: > >> In response to Per olof Ljungmark <peo@intersonic.se>: > >>> What is a good way to find out how memory is used? Have a 6.4 box > >>> where memory is used by something but I fail to see what is using it - > >>> tried different switches to ps(1), tried the stat tools but a big > >>> chunk of memory does not show at all. > >>> > >>> A proper tool for analyzing memory usage "live", this is a production > >>> box? > >> > >> I've always been able to get what I need from top. You can do -o res to > >> sort by resident memory usage, which helps. > > > > ps will sort by memory usage when given the -m flag. Also check ipcs -a > > to see if there are any sysv shared memory segments hanging arnound. If > > you don't see anything using the memory, where are you seeing that > > "something" is using it? > > What I see is a slapd process using about 150M, then around a hundred imap > processes 5-10M each. If the server is restarted, 70-80% will be free, > now, after three months we're at 11% free loosing about 20% per month. > > The exact sum VSZ right now as shown by ps is 1073632k but top says > > Mem: 3111M Active, 311M Inact, 230M Wired, 144M Cache, 112M Buf, 27M Free > > Clearly something is grabbing memory and not releasing it. Disk cache, most likely. I would expect "Free" memory as reported by top to drop down to under 100MB a few hours after a system is rebooted. The difference between Active->Inact->Cache->Buf is more an indication of how long ago a particular page has been touched (and how much work it is to map the page back into a processes memory space), and doesn't really say what the block is being used for. If you are not actively swapping, there is no need for panic. Even a couple hundred MB of used swap is fine, as long as you're not constantly having to pull it back into memory. http://www.freebsd.org/doc/en/books/arch-handbook/vm.html has a good rundown of how the VM system works. -- Dan Nelson dnelson@allantgroup.com
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20090902031626.GD2855>