Where has all the freemem gone?
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From: Casper H.S. Dik on 31 Mar 2010 04:39 Boardy <jonathan.board(a)googlemail.com> writes: >Perhaps I'm tired but... > I have a Solaris 10 server with 32,768MB RAM. > It's running 4 non-global zones. > sar -r reports that it has about 200,000 8KB pages free (1,600MB). > vmstat -p agrees, showing 1,500 to 1,600MB free. > This would suggest that I've used 31,000MB of RAM > Looking at prstat -Z -s rss I can only account for about 6,500MB >So where has all the freemem gone? The kernel will use all memory for caching or other memory uses. "Free memory" is wasted memory; all files access will be cached until the memory is needed somewhere else. Casper -- Expressed in this posting are my opinions. They are in no way related to opinions held by my employer, Sun Microsystems. Statements on Sun products included here are not gospel and may be fiction rather than truth.
From: Paul Floyd on 31 Mar 2010 15:34 On Tue, 30 Mar 2010 14:59:42 -0700 (PDT), Boardy <jonathan.board(a)googlemail.com> wrote: >> >> > So where has all the freemem gone? >> >> Lurking backstage until its required! �Freed pages are reclaimed when >> required. �If you are using ZFS, it will be using free memory for its cache. >> > > This makes monitoring the amount of freemem a bit pointless. > Is there a better way to keep an eye on the systems virtual and > physical memory? > Is there a way to force the pages to be reclaimed? > Is there a way to determine how much the ZFS cache is using? Personally, I'd say that the most important thing (for VM) is the number of page-ins and page-outs. If these are high, it means that the machine is thrashing. If they are low, then the machine will be running (or idling) as fast as possible. A bientot Paul -- Paul Floyd http://paulf.free.fr
From: Michael Laajanen on 31 Mar 2010 16:52 Hi, Boardy wrote: >>> So where has all the freemem gone? >> Lurking backstage until its required! Freed pages are reclaimed when >> required. If you are using ZFS, it will be using free memory for its cache. >> > > This makes monitoring the amount of freemem a bit pointless. > Is there a better way to keep an eye on the systems virtual and > physical memory? I always use vmstat like you but vmstat 1 and the I watch of I have extensive eactivity on the sr field. Probably someone better than me here can tell if that is a good way or not for determan if memory is a problem or not, just like if CPUs is a problem or not. > Is there a way to force the pages to be reclaimed? Probably but when should you do that every second or what? That would work like a garbage collection and possible frezzing the machine from time to time. > Is there a way to determine how much the ZFS cache is using? > /michael
From: Volker Borchert on 31 Mar 2010 16:18 Casper H.S. Dik wrote: > The kernel will use all memory for caching or other memory uses. > > "Free memory" is wasted memory; all files access will be cached until > the memory is needed somewhere else. Does the old rule of thumb "sr > 100 for prolonged periods of time indicates memory shortage" still hold? Perhaps for a value other than 100? -- "I'm a doctor, not a mechanic." Dr Leonard McCoy <mccoy(a)ncc1701.starfleet.fed> "I'm a mechanic, not a doctor." Volker Borchert <v_borchert(a)despammed.com>
From: Darren Dunham on 5 Apr 2010 20:09 On Mar 31, 1:18 pm, v_borch...(a)despammed.com (Volker Borchert) wrote: > Casper H.S. Dik wrote: > > The kernel will use all memory for caching or other memory uses. > > > "Free memory" is wasted memory; all files access will be cached until > > the memory is needed somewhere else. > > Does the old rule of thumb > "sr > 100 for prolonged periods of time indicates memory shortage" > still hold? Perhaps for a value other than 100? No, that's a pre-Solaris 8 figure. Since Solaris 8, the page scanner should never run unless you have a memory shortfall. Well, I guess if you consider 0 just a different value than 100, then yes. But that old figure was wrong in so many ways. -- Darren
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