How can I determine/increase ramsize?

Supriya Sriraman sriraman.supriya at gmail.com
Thu Jan 11 00:09:53 UTC 2007


I want to determine and increase ram size on RHEL 4.

Can anyone help me with this?

I need 96MB, so I used a bs of 1024 and count of 93750 for the dd command.
It failed.

FAILS (RHEL 4)
==============
dd if=/dev/zero of=/dev/ram1 bs=1024 count=93750
dd: writing `/dev/ram1': No space left on device
16385+0 records in
16384+0 records out

dd if=/dev/zero of=/dev/ram1 bs=1024 count=16385
dd: writing `/dev/ram1': No space left on device
16385+0 records in
16384+0 records out

Count of 16384 works, but nothing higher does.

WORKS (RHEL 4)
==============
dd if=/dev/zero of=/dev/ram1 bs=1024 count=16384
16384+0 records in
16384+0 records out

dd if=/dev/zero of=/dev/ram2 bs=1024 count=16384
16384+0 records in
16384+0 records out

$ cat /proc/meminfo
MemTotal:     16574352 kB
MemFree:      14907316 kB
Buffers:        253092 kB
Cached:         729308 kB
SwapCached:        140 kB
Active:         865416 kB
Inactive:       272900 kB
HighTotal:    15794176 kB
HighFree:     14891264 kB
LowTotal:       780176 kB
LowFree:         16052 kB
SwapTotal:    20414456 kB
SwapFree:     20414316 kB
Dirty:               8 kB
Writeback:           0 kB
Mapped:         195864 kB
Slab:           496572 kB
CommitLimit:  28701632 kB
Committed_AS:   447724 kB
PageTables:       5084 kB
VmallocTotal:   106488 kB
VmallocUsed:     12016 kB
VmallocChunk:    94152 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:     2048 kB
$ free
             total       used       free     shared    buffers     cached
Mem:      16574352    1667100   14907252          0     253092     729308
-/+ buffers/cache:     684700   15889652
Swap:     20414456        140   20414316

I have a machine with a Debian distribution on which the dd command with
bs=1024 count=93750:

DEBIAN:
dd if=/dev/zero of=/dev/ram1 bs=1024 count=93750
93750+0 records in
93750+0 records out


$ cat
/proc/meminfo

        total:    used:    free:  shared: buffers:  cached:
Mem:  1585790976 1579163648  6627328        0 33210368 1361088512
Swap: 1073733632 14704640 1059028992
MemTotal:      1548624 kB
MemFree:          6472 kB
MemShared:           0 kB
Buffers:         32432 kB
Cached:        1327956 kB
SwapCached:       1232 kB
Active:         938112 kB
Inactive:       428852 kB
HighTotal:     1048576 kB
HighFree:         2860 kB
LowTotal:       500048 kB
LowFree:          3612 kB
SwapTotal:     1048568 kB
SwapFree:      1034208 kB
$
free

             total       used       free     shared    buffers     cached
Mem:       1548624    1542228       6396          0      32432    1328008
-/+ buffers/cache:     181788    1366836
Swap:      1048568      14360    1034208


Thanks!



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