Messages in this thread | | | Date | Wed, 9 Feb 2000 14:27:15 +0100 (CET) | From | Rik van Riel <> | Subject | Re: Kernel memory allocation for FS in the presence of intensive processes |
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On Wed, 9 Feb 2000, Jeff Waller wrote:
> I noted that the kernel I am currently using 2.2.14 + DVD patches > preformed poorly when attempting to play DVD's. Poorly in that the > Xerver becomes unresponsive to mouse motion, remote logins hang. > The disk goes crazy, basically, I think the system is thrashing.
Very much likely. Virtual memory in 2.2 sucks. We hope to have it mostly fixed in 2.2.15 (current prepatch level pre-7, get it from ftp://ftp.kernel.org/pub/linux/kernel/people/alan/).
I'd like to hear how that prepatch performs for you. If it still sucks in certain situations I'll see what I can do...
> It appeared that Xwindows without the DVD-related software > running (or ever having run) takes about 55 M.
The critical word here is "appeared". The X server usually maps in all the video card memory and a half-dozen libraries. All of those count towards the size of the program, even though not all of them are memory resident.
> But afterwords, top reports an anomalous amount of memory > being used. Apparently by the kernel...Apparently. As a test > I tried (after rebooting) > > find /dvd -type f -exec cat {} > /dev/null \; > > Thinking that perhaps the kernel was allocating memory but > not releasing it and in fact all free memory was "used up" > at least by what top reports.
The kernel keeps disk buffers around, freeing them when memory is needed again. Free memory is wasted memory... (mainly because reading things in from disk is about 100.000 times slower than reading from RAM and we can free the memory fast enough when we need it again)
> Could you suggest where I can delve deeper? Is this a > known problem?
It's a known problem and we hope to have solved it in kernel version 2.2.15.
regards,
Rik -- The Internet is not a network of computers. It is a network of people. That is its real strength.
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