> -----Original Message----- > From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On > Behalf Of Keith Keller > Sent: Monday, July 12, 2010 10:41 AM > To: CentOS mailing list > Subject: Re: [CentOS] free > > On Mon, Jul 12, 2010 at 10:15:06AM -0400, Jason Pyeron wrote: > > The man page does not say much, but does this mean I have only 396668 > > used by programs (used-cached)? > > > > Or shoul I be reading the 2nd line? > > Yes, you should be reading the second line. > > > [root at ten-212 ~]# free > > total used free shared buffers > cached > > Mem: 7918844 5478820 2440024 0 111684 > 5082152 > > -/+ buffers/cache: 284984 7633860 > > Swap: 9961464 204 9961260 > > This first line includes all files that are being cached in memory (for > faster reading if needed later, for example). That memory will be > freed up if needed. The second line doesn't include that cache, so is > a better indicator of actual memory use. > > (And on that first line, "cached" is already part of "used", so your > free memory counting the cache is 2440024; it's just provided for > informational purposes.) I did some testing a while back, and my results showed that the -/+ buffers line seemed to be the *Minimum* amount of ram available if the kernel purged it's buffers/cache. Sometimes more is available. (Roughly) The test was: * Turn swap off * Run free * Run 20 instances of a test program that malloc'd 100 megs of ram * Run free, see 2 gigs of ram + orginal amount of ram used. * Kill N number of those programs, which should free up N*100megs * Run free, output of -/+ did not reflect 2gigs - (N*100 megs). I followed up by running enough instances of the test program that I should have run out of memory free said I had, but the programs all started, none were killed. I ran free again got a number pretty close to what I thought should be free. It's a fun test to play with, I assume results vary from kernel to kernel (how aggressive the kernel is cleaning up returned ram). Patrick