Free V SAR

[Duffs]

Hi,

I had a server that experienced a crash last night and when I looked at the SAR report it showed that the "%memused" was 98%. On comparing this today with the memory info displayed from the "free" command, there appears to be a considerable difference (See below). Can anybody explain what the difference is between the two and what is the true reflection of what memory the box is using?

# sar -r -f /var/log/sa/sa23 (shows "memused" @ 79%:

03:35:01 PM kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree kbswpused %swpused kbswpcad
03:40:01 PM 9198600 56784520 86.06 630044 21133808 65535992 0 0.00 0
03:45:01 PM 9195232 56787888 86.06 630292 21134048 65535992 0 0.00 0
03:50:01 PM 9170532 56812588 86.10 630584 21133872 65535992 0 0.00 0
03:55:01 PM 9149868 56833252 86.13 630856 21134152 65535992 0 0.00 0
Average: 13659699 52323421 79.30 554684 19173568 65535992 0 0.00 0

However free only suggests that the box is using 53%:

[root@fworksdb2 ~]# free -b|grep ^-|awk '{ print (($3/($3+$4))*100) "% Used" }'
53.1834% Used

Rgds,
D.

[Tim Nelson]

keep in mind that the first line of free command includes the allocated cache.

linux will use all available mem for cache and give back as needed.


look at the -/+ buffers/cache line for the real numbers.