top or htop? Which one lies?
fatgerman at ntlworld.com
Sun Nov 8 12:29:28 GMT 2009
On Sunday 08 Nov 2009 08:55:08 Chris Jones wrote:
> On 7 Nov 2009, at 10:54pm, Mark Greenwood wrote:
> > I hope someone on here can clear this up.
> > According to top my RAM is as follows:
> > 2060580k total, 1866728k used, (which seems to me to be a
> > ridiculously enormous amount of RAM to run a bare desktop)
> > According to htop (which I can't copy and paste)
> > 269/2012MB (which seems to me to be a quite miraculously small
> > amount of RAM to run a bare desktop)
> > Which one lies? And why the mahoosive discrepancy?
> Neither. The difference is almost certainly the file cache.
> ram access is much faster that disk access, and your linux kernel
> knows this, so will use any 'unused' ram as a cache of all recently
> accessed files, just in case you need them again. This means most
> linux system will, after some time of usage, use what might seem like
> a surprising large amount of ram, even when you aren't actually
> running any applications.
> The confusion comes because some ways of monitoring memory usage
> include the file cache, others don't, since the ram used for the file
> cache is only used as long as it is not needed for any other usage. As
> soon as it is needed it will be given back. For me, the clearest
> utility is the command line 'free' command.
> So, my bet is your system is using 269MB of ram for real data storage,
> and the difference between this and 1867MB is the file cache...
Thanks Guys, I knew there were never any simple answers :)
'free' gives me:
total used free shared buffers cached
Mem: 2060580 575336 1485244 0 27332 258848
-/+ buffers/cache: 289156 1771424
Swap: 6032368 0 6032368
Which appears to say I have 575336 (KB?) of RAM used, which is closer to what top is telling me today than to what htop is telling me. Another day, 3 different numbers :) Still at least you've cleared up my concern, I know what all that memory is being used for even if I don't know how much :-D
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