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When I am running top command (on embedded system with 64 MB RAM) I am getting below description on total memory usage:

"Mem: 43468K used, 968K free, 0K shrd, 1280K buff, 21896K cached"

It looks like I have only 968 KB of ram free. But meanwhile I can see 21896KB in cache. Can I allocate (malloc) more than 968 from an application meantime ? If I do so, will the ram be reclaimed from cache ?

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Linux will use available memory for disk caching, unless it's required by a running program. So your you can allocate (used - cached + free) amount of memory, in your case, 43468 - 21896 + 968

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