tag 596865 + moreinfo
kthxbye
Hi,
Simon Waters wrote:
Package: dphys-swapfile
Version: 20061020-1
Severity: normal
Subject: dphys-swapfile: Memory calculation is wrong for AMD 64bit systems
As noted in bug 564466 [...]
While the subject of your bug report suggests that you are reporting
the same issue as #564466, the fact that you seem to know about that
bug makes me wonder what kind of problem you really try to report, as
the remainder of your report just seems to document some details of
the already fixed issue of #564466 (http://bugs.debian.org/564466):
on AMD 64 systems the /proc/kcore size is reported as excessively
large due to the handling of vmalloc on that platform.
The kernel documentation was in error, claiming that kcore would be
size of memory with a small adjustment when it is (now at least)
more complex than that.
If we must rely on /proc interface then the second field of the
first line of /proc/meminfo contains size of RAM. As per changes
below, however I'm not sure if relying on /proc is a good idea, I
haven't checked kernel source to see if it is always the first line,
or if the unit field is hard coded. So probably wise to make a more
robust case than this.
I'm still trying to understand fully how AMD64 handles memory usage
so probably wise to run this past someone who does understand the
topic better.
In 20061020-3 this is solved as follows:
# this seems to be the nearest to physical RAM size, lacks about 60k
# but it actually then fails from AMD64 kernel 2.6.32 onwards
#KCORESIZE=`ls -l /proc/kcore | awk '{ print $5 }'`
## make MBytes which rounded down will be exactly 1 too few, so add 1
#MEMSIZE=`expr ${KCORESIZE} / 1048576 + 1`
# so second attempt at finding out physical RAM size, lacks about 10M
# see how long this variant stays usable :-)
MEMTOTAL=`grep '^MemTotal:' /proc/meminfo | awk '{ print $2 }'`
# make MBytes which rounded down will be about 10 too few, so add 10
MEMSIZE=`expr ${MEMTOTAL} / 1024 + 10`
Regards, Axel
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