[gentoo-dev] Re: Optimizing performance

[Duncan <1i5t5.duncan@cox.net>]

Paul de Vrieze posted <200512271638.22215.pauldv@gentoo.org>, excerpted
below,  on Tue, 27 Dec 2005 16:38:21 +0100:

> On Saturday 24 December 2005 00:52, Diego 'Flameeyes' Pettenò wrote:
>> On Friday 23 December 2005 18:35, Paul de Vrieze wrote:
>> > Just to add. This is not so much related to debugging information in
>> > the library files (what gdb can use). That information never makes it
>> > from disk so is not that much of a speed issue (esp. if it is split
>> > out).
>>
>> Actually, if the binaries are not stripped, they consume more memory.
>> With splitdebug the issue is unseen (I'm happily using it with -g3 for
>> everything now..)
> 
> Debug info shouldn't be loaded into memory. Or is it? I agree though that
> splitting them out is probably better for memory use.

>From what I've read, binary files are read into memory as a file, before
being having their elements loaded at specific addresses by ldd.  Unsplit
debug information at minimum, then, increases the i/o load, requiring more
data be read into memory initially, even if it's immediately thrown out
again, when it's not actually loaded anywhere.  In practice, it would at
least remain in cache rather longer, thereby taking up space that could be
used to cache data that might actually be used, not to mention forcing
other potentially useful data out of cache on initial read into cache.

Debug information split into entirely separate files, then, shouldn't
affect performance at all over stripped, and be rather better performing
than debug information stored in the same file.

That's only what I've read.  I have no special knowledge on the subject,
and if what I read was incorrect, than so is the above.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


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