Julian Elischer <[EMAIL PROTECTED]> writes:
> check out /proc/<PID>/map for a really detailed map of the process.
That looks good for a single process, suffers from the problem I'm
having. For example, if I run a program that simply mallocs a chumk of
memory and reads through it (to map it all in), it's pretty easy to identify
the affected object:
guppy% cat /proc/23072/map
0x8048000 0x8049000 1 0 0xcdd610c0 r-x 1 0 0x0 COW NC vnode
0x8049000 0x804a000 1 0 0xce619060 rw- 2 0 0x2180 NCOW NNC default
0x804a000 0xc04b000 16385 0 0xce619060 rwx 2 0 0x2180 NCOW NNC default
...
But after sleeping for a bit, the program then forks, and I have two
processes sharing the same memory. I hope to see something that reflects
this, but:
guppy% cat /proc/23072/map
0x8048000 0x8049000 1 0 0xcdd610c0 r-x 2 0 0x0 COW NC vnode
0x8049000 0x804a000 1 0 0xcdc84360 rw- 2 0 0x180 COW NC default
0x804a000 0xc04b000 16385 0 0xce619060 rwx 2 0 0x180 COW NC default
...
guppy% cat /proc/23074/map
0x8048000 0x8049000 1 0 0xcdd610c0 r-x 2 0 0x0 COW NC vnode
0x8049000 0x804a000 1 0 0xcdc84360 rw- 2 0 0x180 COW NC default
0x804a000 0xc04b000 16385 0 0xce619060 rwx 2 0 0x180 COW NC default
...
The object's ref_count hasn't changed, which is what I meant about seeing
reference counts in the kernel that were apparently not counting what I'm
looking for. I did see a ref_count increase on the first object
(presumably the text image), but nothing on the allocated memory.
It seems the object level isn't fine enough, but the deeper I go into the
VM code, the more confused I become. In this forked process example, what
happens when I alter a few COW pages in the currently-shared object?
Apparently a shadow object is created, but it claims to be the same size as
the original object. True, but I know it's not actually using that many
pages, since most of them are still validly shared. System usage numbers
tell me this is true, but I can't find what in the process or object data
structures reflect this fact.
- Jamie
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message
