linux-kernel - Re: [KORG] Re: kernel.org lies about latest -mm kernel

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Date:	Sat, 6 Jan 2007 20:35:10 +0100
From:	Willy Tarreau <w@....eu>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>,
	"J.H." <warthog9@...nel.org>, Andrew Morton <akpm@...l.org>,
	Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	webmaster@...nel.org
Subject: Re: [KORG] Re: kernel.org lies about latest -mm kernel

On Sat, Jan 06, 2007 at 11:18:37AM -0800, H. Peter Anvin wrote:
> Randy Dunlap wrote:
> >
> >>>BTW, yesterday my 2.4 patches were not published, but I noticed that
> >>>they were not even signed not bziped on hera. At first I simply thought
> >>>it was related, but right now I have a doubt. Maybe the automatic script
> >>>has been temporarily been disabled on hera too ?
> >>The script that deals with the uploads also deals with the packaging -
> >>so yes the problem is related.
> >
> >and with the finger_banner and version info on www.kernel.org page?
> 
> Yes, they're all connected.
> 
> The load on *both* machines were up above the 300s yesterday, probably 
> due to the release of a new Knoppix DVD.

I have one trivial idea : would it help to use 2 addresses to server data,
one for pure kernel usage (eg: git, rsync) and one with other stuff such
as DVDs, but with a low limit on the number of concurrent connections ?

> The most fundamental problem seems to be that I can't tell currnt Linux 
> kernels that the dcache/icache is precious, and that it's way too eager 
> to dump dcache and icache in favour of data blocks.  If I could do that, 
> this problem would be much, much smaller.

I often have this problem on some of my machines after slocate runs.
Everything is consumed in dcache/icache and no data blocks are cacheable
anymore. I never found a way to tell the kernel to assign a higher prio
to data than to [di]cache. To remedy this, I wrote this stupid program that
I run when I need to free memory. It does simply allocate the memory size
I ask, which causes a flush of the [di]caches, and when it exits, this
memory is usable again for data blocks. 

I'm not sure it would be easy to automatically run such a thing, but
maybe it could sometimes help when the [id]caches are too fat.

Willy

#include <stdio.h>
main(int argc, char **argv) {
  unsigned long int i,k=0, max;
  char *p;

  max = (argc>1) ? atol(argv[1]) : 102400; // default to 100 MB
  printf("Allocating %lu kB...\n",max);
  while (((p=(char *)malloc(1048576))!=NULL) && (k+1024<=max)) {
    for (i=0;i<256;p[4096*i++]=0); /* mark block dirty */
    k+=1024;
    fprintf(stderr,"\r%d kB allocated",k);
  }
  fprintf(stderr,"\nMemory freed.\n");
  exit(0);
}

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