Re: [Valgrind-developers] What is this failure?

[Eyal L. <ey...@ey...>]

Julian Seward wrote:
> 
> On Thursday 15 January 2004 08:57, Robert Walsh wrote:
> > > However, the same sort of malloc() followed by a free() was
> > > done a number of times earlier. If vg holds on to freed
> > > memory then there may be a problem. The machine is 1GB memory
> > > and 2GB swap and abour 450MB of swap was used at the time
> > > of failure.
> >
> > Valgrind does hold on to memory for a certain length of time after it's
> > been freed.  This is to catch things like this:
> >
> >   x = malloc(10);
> >   free(x);
> >   y = malloc(10);
> >   *x = 0;
> >
> > If the second malloc happed to return the same value as the first, the
> > invalid write to *x would never be caught.
> >
> > However, it doesn't keep these forever, and I had assumed it would use
> > that pool when it ran out of memory.  Hmm.  Too tired to look at the
> > code now, but it's in there somewhere.  Search for freed_list.
> 
> Command-line parameter:
>     --freelist-vol=<number>   volume of freed blocks queue [1000000]

Used '--freelist-vol=0' - no change.

Furthermore, since I know the failure is in a malloc that never
returns, I put a sleep(2) just before the malloc and started a
'vmstat 1'. It fails in the same way and only under 400MB of
swap (out of 2GB) is used max.

Is there any other tracing I can turn on to help diagnose the
problem?

--
Eyal Lebedinsky (ey...@ey...) <http://samba.org/eyal/>