[CentOS] XFS and CentOS 4.3

Aleksandar Milivojevic alex at milivojevic.org
Thu Aug 17 13:55:30 UTC 2006


Quoting Les Mikesell <lesmikesell at gmail.com>:

> Just because you have some memory to spare doesn't mean that
> malloc() can hand you 600 megs of contiguous memory.  And I've
> lost track of what the fashionable way of handling VM is
> now.  Is it the slow but sure "check first and fail if
> impossible" or the fast and dirty "always succeed and worry about
> paging later"?  Or is it user-configurable now?  Usually I just
> allocate 2 gigs of swap on the theory that if it goes that far the
> machine will be so unresponsive I'll think it's dead anyway.

I beleive it is the "lazy" system, where request for memory allocation  
is always successfull, and the app gets killed if there is not enough  
backing store later.  I know this is configurable parameter in Tru64  
and Solaris.  Not sure if it is configurable parameter in Linux.

However, the thing is, there was enough free swap space to handle  
things.  More than 1 gig of free swap space, that is.  There was  
enough free swap to move *everything* that was in physical RAM onto  
it, if needed.  So it wasn't the case of "ran out of free swap".  It  
was a clear failure of VM to utilize the resources it had (real memory  
+ swap space).  The VM should have put things on hold until enough  
pages were swapped out.  Not kill things or deny memory to other  
kernel modules (and in this case, cause file system corruption).

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