Caching of object/libraries/files

Caching of object/libraries/files

[Nick Savoiu]

Hi all,

I have a rather large project composed of a small driver executable and
quite a few .so libraries that it uses.

When I invoke it with GDB, upon executing 'run' it takes quite a while for
GDB to do it's thing (i.e. load symbols, whatever else it does) particularly
since it does a lot of disk access.

I was thinking that, if I start a GDB session on this project, run it for a
while then quit and immediately restart a similar session, then most of the
files would be cached. However, I see the same amount of disk access for the
second session when 'run' is invoked as for the first.

Any ideas why this is so? The GDB session itself uses about 340MB and I have
1GB RAM.

Thanks,
Nick

Re: Caching of object/libraries/files

[Daniel Jacobowitz]

On Thu, Mar 18, 2004 at 10:46:47AM -0800, Nick Savoiu wrote:
> Hi all,
> 
> I have a rather large project composed of a small driver executable and
> quite a few .so libraries that it uses.
> 
> When I invoke it with GDB, upon executing 'run' it takes quite a while for
> GDB to do it's thing (i.e. load symbols, whatever else it does) particularly
> since it does a lot of disk access.
> 
> I was thinking that, if I start a GDB session on this project, run it for a
> while then quit and immediately restart a similar session, then most of the
> files would be cached. However, I see the same amount of disk access for the
> second session when 'run' is invoked as for the first.
> 
> Any ideas why this is so? The GDB session itself uses about 340MB and I have
> 1GB RAM.

This is something that I've been meaning to fix for a long, long time. 
We unload all shared objects when the program exits; what we ought to
do is move them to a separate cache structure.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

Re: Caching of object/libraries/files

[Nick Savoiu]

> On Thu, Mar 18, 2004 at 10:46:47AM -0800, Nick Savoiu wrote:
> > Hi all,
> >
> > I have a rather large project composed of a small driver executable and
> > quite a few .so libraries that it uses.
> >
> > When I invoke it with GDB, upon executing 'run' it takes quite a while
for
> > GDB to do it's thing (i.e. load symbols, whatever else it does)
particularly
> > since it does a lot of disk access.
> >
> > I was thinking that, if I start a GDB session on this project, run it
for a
> > while then quit and immediately restart a similar session, then most of
the
> > files would be cached. However, I see the same amount of disk access for
the
> > second session when 'run' is invoked as for the first.
> >
> > Any ideas why this is so? The GDB session itself uses about 340MB and I
have
> > 1GB RAM.
>
> This is something that I've been meaning to fix for a long, long time.
> We unload all shared objects when the program exits; what we ought to
> do is move them to a separate cache structure.

That would be an immense help. Staring idly at the screen was never my idea
of a good time :)

Any idea when this could get fixed?

Nick

Re: Caching of object/libraries/files

[Nick Savoiu]

The problem that I have is that after I run gdb once, exit it then start it 
right after it seems to reload all the debug info from disk. I was expecting 
a good deal of them to be loaded from the OS file cache -> much less disk 
activity the second time around.

Nick

> On Thu, Mar 18, 2004 at 10:46:47AM -0800, Nick Savoiu wrote:
> > Hi all,
> > 
> > I have a rather large project composed of a small driver executable and
> > quite a few .so libraries that it uses.
> > 
> > When I invoke it with GDB, upon executing 'run' it takes quite a while for
> > GDB to do it's thing (i.e. load symbols, whatever else it does) 
particularly
> > since it does a lot of disk access.
> > 
> > I was thinking that, if I start a GDB session on this project, run it for 
a
> > while then quit and immediately restart a similar session, then most of 
the
> > files would be cached. However, I see the same amount of disk access for 
the
> > second session when 'run' is invoked as for the first.
> > 
> > Any ideas why this is so? The GDB session itself uses about 340MB and I 
have
> > 1GB RAM.
> 
> This is something that I've been meaning to fix for a long, long time. 
> We unload all shared objects when the program exits; what we ought to
> do is move them to a separate cache structure.