Linux Kernel 2.2.19 Available Memory Bug

Linux Kernel 2.2.19 Available Memory Bug

[John L. Males]

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Hello,

Please note I am not on the Kernel Mailing List so do try to copy me
in with any reply, questions, clarifications, confirmations, et al on
this bug report.

Before I forget I am using SuSE 6.4 with most of the updates from the
base applied, most meaning I generally lag a bit behind at times.  I
am NOT using the SuSE kernel due to bugs introduced into the SuSE
kernel with the SuSE patches/enhancements.  I am using the Linus
2.2.19 Kernel with the OpenWall patches.  System is AMD K6-2 500
based system.  The version of gcc was 2.95.2 to compile the kernel.

The bug I am reporting is that when one sets the amount of memory,
i.e. 128M, 256M; at the time of booting the 2.2.19 kernel the "Total
Memory" as reported by KDE, "free", etc is short by a important
amount.  To be more specific I will detail the results of "free"
below against the "mem" value passed to the kernel.  Please note for
the purposes of this test I always had 256MB or ram (2x128MB)
installed in my system.  The BIOS reports total system memory as
262144K.

"mem=256m"
***************

KDE reports 251.09 Total System memory, or 263290880 bytes.

"free -m" indicates "Total Memory" as 251
"free -k" indicates "Total Memory" as 257120
"free -k" indicates "Total Memory" as 263290880

The exact same vaules as noted above are indicated for "mem=262144k",
and "mem=268435546" (256 X 1024 x 1024).

"mem=128m"
***************

"free -m" indicates "Total Memory" as 124
"free -k" indicates "Total Memory" as 127344
"free -k" indicates "Total Memory" as 130400256


Regards,

John L. Males
Software I.Q. Consulting
Toronto, Ontario
Canada
20 July 2001 03:47
mailto:software_iq@TheOffice.net
mailto:jlmales@softhome.net

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Re: Linux Kernel 2.2.19 Available Memory Bug

[Doug McNaught]

"John L. Males" <software_iq@TheOffice.net> writes:

> The bug I am reporting is that when one sets the amount of memory,
> i.e. 128M, 256M; at the time of booting the 2.2.19 kernel the "Total
> Memory" as reported by KDE, "free", etc is short by a important
> amount.  To be more specific I will detail the results of "free"
> below against the "mem" value passed to the kernel.  Please note for
> the purposes of this test I always had 256MB or ram (2x128MB)
> installed in my system.  The BIOS reports total system memory as
> 262144K.

Not really a bug--the "free" report leaves out the memory devoted to
the kernel, which is unpageable and therefore unavailable to user
apps. 

-Doug
-- 
The rain man gave me two cures; he said jump right in,
The first was Texas medicine--the second was just railroad gin,
And like a fool I mixed them, and it strangled up my mind,
Now people just get uglier, and I got no sense of time...          --Dylan