I have a huge RAM-consuming Java process and I'm trying to figure what he's doing with all this memory. So, I'm doing a pmap -x on this PID and here is a piece of the result :

Address           Kbytes     RSS   Dirty Mode   Mapping
0000000000001000       4       0       0 rw---    [ anon ]
0000000000400000      48       0       0 r-x--  java
000000000050b000       4       4       4 rw---  java
0000000003b9d000     264     224     212 rw---    [ anon ]
0000000003bdf000 2199556 1887992 1830160 rw---    [ anon ]
000000396c800000     112     108       0 r-x--  ld-2.5.so
000000396ca1c000       4       4       4 r----  ld-2.5.so
[...]
ffffffffff600000    8192       0       0 -----    [ anon ]
----------------  ------  ------  ------
total kB         7072968 4382820 4270104

As you can see on address 3BDF000 there is a mapping of 2199556 KBytes with 1830160 of Dirty.

In /proc/10139/smaps, on can see it with more details :

03bdf000-89fe0000 rw-p 03bdf000 00:00 0
Size:           2199556 kB
Rss:            1887996 kB
Shared_Clean:         0 kB
Shared_Dirty:         0 kB
Private_Clean:    57832 kB
Private_Dirty:  1830164 kB
Swap:            231996 kB
Pss:            1887996 kB

Hence, I'd like to know what this dirty memory is? I guess these pages don't have to be written to disk, so why are they called dirty?

linux memory-management jvm
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