On Wednesday 09 May 2007 14:20, Registration Account wrote:
> Personally IF the PC has the max amount of physical RAM installed AND
> still requires a Disk I/O to simulate more RAM then we really need to
> think about the fundamental operation of the O/S. How much RAM can it
> directly address and how much RAM does it need to juggle in and then
> does it requires a page file as well - Personally then its time to
> re-write the O/S in its memory management and its directly addressable
> RAM to process and the amount of physical RAM used by the memory manager.
The above paragraph is an over simplification, and not entirely correct
in
general, and not correct at all in terms of Linux. There are legitimate uses
for a swap file... and many linux installations make use of several large
swap files on each machine! My current desk machine has a swap file of 1024M
and real ram of 512M. I will generally set my swap file to twice the size of
main store--- but there is no such fixed rule. Having said that--- most of
the time my machine *never* swaps. I've been watching my new system monitor
(thanks Randall) now most of the afternoon and my machine has not swapped...
not once. As I have used the machine (mostly mail, small compiles, web
research) I have noticed the kernel adjusting my cache and buffer sizes and
moving along quite happily. This in contrast to my old W2000 and NT machines
that would constantly *thrash* after moderate use... this means many page
faults and lots of wasteful disk I/O like you talk about in your article. The
windoze platform has lousy memory management and even worse file system
management. The Linux kernel has *none* of these problems. This is no
exaggeration--- memory management on Linux is comparable to memory management
on MVS/XA, VM, SysV, Sys38, AS400, name it... seriously.
> Page file addressing should be a last resort by the O/S. Adding to an
> overworked disk I/O will slow things down ultimately, however the
> application will never fall over and you will never see the old "out of
> memory" error response which is the only advantage of such an arrangement.
(see above) Paging is used by the Linux kernel on a needs basis--
absolutely.
And, sometimes those needs are very real and quite legitimate. The more you
play around with the Linux kernel the more comfortable you will become of
course, but rest assured--- you're in good hands. Its easy to create stress
scenarios for your machine that will tax memory and force paging... check it
out.
--
Kind regards,
M Harris <><
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