Re: [Fwd: libpng shared memory patch]

[Behdad Esfahbod <behdad cs toronto edu>]

On Sat, 22 Apr 2006, Lubos Lunak wrote:

> > libpng version 1.2.8rel-5 from dapper
> >
> > before:
> >
> > $ objdump -x /usr/lib/libpng.so  | grep data
> >   11 .rodata       00002a00  00021a30  00021a30  00021a30  2**3
> >  18 .data         00000348  00034cd0  00034cd0  00024cd0  2**2
> >   20 .sdata        000000b0  0003502c  0003502c  0002502c  2**2
> >
> > 0x348+0xb0=0x3F8=1016 bytes
> >
> > $ python memstats.py | grep libpng
> > private: /usr/lib/libpng12.so.0.1.2.8: 168 KB (spread among 84 mappings)
>
>  This in other words means that every process has two dirty pages because of
> libpng.

How did you get two pages?  Each process has two mappings for
libpng12.  So with 84 mappings, there are 42 processes, and 168
KB / 42 = 4k = 1 page.


Note that even moving from .data to .rodata is desirable anyway,
even if it doesn't result in reduced memory consumption, it does
result in reduced relocations which is good.


--behdad
http://behdad.org/

"Commandment Three says Do Not Kill, Amendment Two says Blood Will Spill"
	-- Dan Bern, "New American Language"