Re: v2.6.11.8 #3 and v2.6.11.8 #1 tcp_mem strangeness!

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When I check
/tmp/linux-2.6.11.10/Documentation/networking/ip-sysctl.txt I see the
following:

tcp_mem - vector of 3 INTEGERs: min, pressure, max
        low: below this number of pages TCP is not bothered about its
        memory appetite.

        pressure: when amount of memory allocated by TCP exceeds this
        number
        of pages, TCP moderates its memory consumption and enters
        memory
        pressure mode, which is exited when memory consumption falls
        under "low".

        high: number of pages allowed for queueing by all TCP sockets.

        Defaults are calculated at boot time from amount of available
        memory.
Since a page is 4096 bytes on the i386, I did the following:

(98304*4096)/(1024*1024)
384

I am missing something ???


Thanks
Paul


On Fri, May 20, 2005 at 01:35:55PM -0500, Eric Bambach wrote:
> Im pretty sure those numbers are expressed in kb, not mb. So if they are in kb 
> does it still matter what the calculation is or are you trying to do some 
> more tuning?
> 
> On Friday 20 May 2005 12:01 pm, Paul Griffith wrote:
> > Greetings,
> >
> > Hardware:
> > P4/2.8Ghz/1GB/40GB HDD/G4 FX5200
> > Intel 865PERL
> >
> > 1) When I boot with v2.4.29 on my local computer tcp_mem set to the
> > following: cat /proc/sys/net/ipv4/tcp_mem
> > 49152   65536   98304
> > (192MB)  (256MB)  (384MB)
> >
> > 2) When I boot the same computer with Knoppix v3.8.2 - v2.6.11.8 #3
> > cat /proc/sys/net/ipv4/tcp_mem
> > 196608   262144  393216
> > (768MB)  (1024MB) (1536MB)
> >
> > 3) When I boot the same computer with Slax v5.0.5 - v2.6.11.8 #1
> > cat /proc/sys/net/ipv4/tcp_mem
> > 98304   131073   196608
> > (384MB) (512MB)  (768MB)
> >
> > I can understand the change in the tcp stack from 2.4.x to 2.6.x. What
> > I don't understand is why one level of the 2.6.11.8 #3 kernel will set
> > my max TCP_MEM to 1.5 * MEMORY and the other 2.6.11.8 #1 sets TCP_MEM
> > to .75 * MEMORY.
> >
> > Anyone one has any idea what is going on here???
> >
> > I am trying to understand the tcp stack in Linux because I have to
> > tune a GigE Linux based NFS/SMB server to as our departmental fileserver.
> > The server is currently using the default tcp settings on 2.4.26
> > [patched to support quotas on RiserFS].
> >
> > Thanks
> > Paul
> > -
> > : send the line "unsubscribe linux-net" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> -- 
> ----------------------------------------
> --EB
> 
> > All is fine except that I can reliably "oops" it simply by trying to read
> > from /proc/apm (e.g. cat /proc/apm).
> > oops output and ksymoops-2.3.4 output is attached.
> > Is there anything else I can contribute?
> 
> The latitude and longtitude of the bios writers current position, and
> a ballistic missile.
> 
>                 --Alan Cox LKML-December 08,2000 
> 
> ----------------------------------------

-- 
Paul Griffith     | York University, Dept. of Computer Science & Engineering
CSE Technical Team| 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3
paulg@xxxxxxxxxxx | CSEB 1003A | Phone: 416-736-2100 x70258 | Fax: 416-736-5872
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