Re: RH30: Virtual Mem shot heavily by locale-archive...

[Brian Gerst <bgerst@didntduck.org>]

Arijit Das wrote:
> I have RH3.0 installed in an AMD64 machine. 
>  
> In this system, when I look at the virtual address space mappings of a process (say a sleep process), I find that almost 80% of its virtual address space has been taken by a private copy of /usr/lib/locale/locale-archive mapped to its virtual address space by default. Check this:
>  
>      31396 KB    r--p    /usr/lib/locale/locale-archive
>  

Only the pages of the file that are actually accessed are loaded into 
physical memory.  This mapping just reserves a slot of virtual memory 
for those demand loaded pages to be mapped.

> Total Virtual Memory = 38816 KB
> On the other hand, when I look at the same info in a RH7.2 system, I see that a few small set of essential locale files have been mapped whose overall summed up size is around 236KB (way smaller than RH3.0)...Check this: 
>          4    r--p    /usr/lib/locale/en_US/LC_IDENTIFICATION
>          4    r--p    /usr/lib/locale/en_US/LC_MEASUREMENT
>          4    r--p    /usr/lib/locale/en_US/LC_TELEPHONE
>          4    r--p    /usr/lib/locale/en_US/LC_ADDRESS
>          4    r--p    /usr/lib/locale/en_US/LC_NAME
>          4    r--p    /usr/lib/locale/en_US/LC_PAPER
>          4    r--p    /usr/lib/locale/en_US/LC_MESSAGES/SYS_LC_MESSAGES
>          4    r--p    /usr/lib/locale/en_US/LC_MONETARY
>         24    r--p    /usr/lib/locale/en_US/LC_COLLATE
>          4    r--p    /usr/lib/locale/en_US/LC_TIME
>          4    r--p    /usr/lib/locale/en_US/LC_NUMERIC
>        172    r--p    /usr/lib/locale/en_US/LC_CTYPE
> This seems like a huge requirement of memory for each small process executed in the RH3.0 system and hence, shots up the memory requirement of the entire system because the mapped region /usr/lib/locale/locale-archive is privately mapped.

Private mapping means copy-on-write.  But since these mappings are 
read-only they will still be shared by other users of that file.  So no 
extra physical memory for each process mapping the file.

--
				Brian Gerst
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