Re: 2.6.1 slower than 2.4, smp/scsi/sw-raid/reiserfs

[Nick Piggin]

Philip Martin wrote:

> Nick Piggin <piggin@xxxxxxxxxxxxxxx> writes:
>
>
> > Another thing I just saw - you've got quite a lot of memory in
> > buffers which might be something going wrong.
> >
> > When the build finishes and there is no other activity, can you
> > try applying anonymous memory pressure until it starts swapping
> > to see if everything gets reclaimed properly?
>
> How do I apply anonymous memory pressure?

Well just run something that uses a lot of memory and doesn't
do much else. Run a few of these if you like:

#include <stdlib.h>
#include <unistd.h>
#define MEMSZ (64 * 1024 * 1024)
int main(void)
{
   int i;
   char *mem = malloc(MEMSZ);
   for (i = 0; i < MEMSZ; i+=4096)
      mem[i] = i;
   sleep(60);
   return 0;
}

> > Was each kernel freshly booted and without background activity
> > before each compile?
>
> Each kernel was freshly booted.  There were a number of daemons
> running, and I was running X, but these don't appear to use much
> memory or CPU and the network was disconnected.  Just after a boot
> there is lots of free memory, but in normal operation the machine uses
> its memory, so to make it more like normal I ran "find | grep" before
> doing the build.  Then I ran make clean, make, make clean, make and
> took numbers for the second make.
>
> You can have the numbers straight after a boot as well.  In this case
> I rebooted, logged in, ran make clean and make -j4.
>
> I can hear disk activity on this machine. During a 2.4.24 build the
> activity happens in short bursts a few seconds apart.  During a 2.6.1
> build it sounds as if there is more activity, with each burst of
> activity being a little longer.  However that just the impression I
> get, I haven't tried timing anything, I may be imagining it.

Thanks. Much the same, isn't it?
Can you try booting with the kernel argument: elevator=deadline
and see how 2.6 goes?

Andrew, any other ideas?

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