dccd memory usage

Roy Bixler rcb@press.uchicago.edu
Tue Oct 5 16:15:34 UTC 2004

On Tuesday 05 October 2004 09:07 am, Vernon Schryver wrote:
> On the contrary, most modern free UNIX systems are absolutely terrible
> in how they handle their disk caches for large files.  They generally
> do no have unified page and file caches, but prefer to pump pages among
> disk files, swap, buffer cache, and VM.  They generally cannot be
> convinced to swap directly to and from memory mapped files, which is
> why many regularly stall and busily pump pages of the DCC database
> among RAM, the DCC files, and swap space!  Linux is particularly bad
> in this area.

I used to notice this in using earlier versions of Linux 2.x.y, where x<6, 
kernels even with ordinary desktop loads.    I understand that in the Linux 
2.6 series that they have actually implemented a unified buffer cache in the 
VM system.  In each case, where x<6 and y is maximal (i.e. the latest version 
of that series), the memory management performance is greatly improved over 
the earlier versions.  I don't run a DCC server, but you may want to try 
upgrading to the latest Linux kernel to see if that helps.  I have also tried 
FreeBSD and that also solved the problem.

Roy Bixler <rcb@press.uchicago.edu>
The University of Chicago Press
http://www.press.uchicago.edu -or- http://www.journals.uchicago.edu

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