On Monday 04 May 2009 21:12:15 Chet Ramey wrote:
> Mike Frysinger wrote:
> > On Thursday 30 April 2009 05:56:02 Jan Schampera wrote:
> >> Sandino Araico Sánchez wrote:
> >>> 1.
> >>> #!/bin/bash
> >>> 2.
> >>>
> >>> 3.
> >>> for i in {0..150000000} ; do
> >>> 4.
> >>> echo $i > /dev/null
> >>> 5.
> >>> done
> >>>
> >>>
> >>>
> >>> Repeat-By:
> >>> Run the script above and the process starts leaking memory very
> >>> fast.
> >>
> >> You know what a memory *leak* is, yes? mallocs() without proper free()s.
> >>
> >> What you mean is that your memory is used. Feel free to calculate the
> >> memory that is needed to store the string representation of
> >> {0..150000000}, I think you will get a number near your RAM size.
> >
> > granted his example is wrong and his reasoning incorrect, there may
> > actually be a leak here ...
> >
> > bash-4.0$ ps -p $$ -F
> > UID PID PPID C SZ RSS PSR STIME TTY TIME CMD
> > vapier 27999 16493 0 5675 3052 1 18:51 pts/1 00:00:00 bash
> > --norc bash-4.0$ for n in {0..150000000} ; do echo $n; done
> > <wait a few seconds>^C
> > bash-4.0$ ps -p $$ -F
> > UID PID PPID C SZ RSS PSR STIME TTY TIME CMD
> > vapier 27999 16493 17 392694 473236 1 18:51 pts/1 00:00:01 bash
> > --norc
> >
> > that memory never goes away and bash will chew significant CPU (~10%)
> > while it should be idle ...
>
> That's not a memory leak. Malloc implementations need not release
> memory back to the kernel; the bash malloc (and others) do so only
> under limited circumstances. Memory obtained from the kernel using
> mmap or sbrk and kept in a cache by a malloc implementation doesn't
> constitute a leak. A leak is memory for which there is no longer a
> handle, by the application or by malloc itself.yes, i know what a leak is, but i hadnt thought of the glibc allocator caching the memory itself. i imagine the cpu usage is simply the glibc allocator walking its internal structures. i also dont really care enough about the issue to prove whether it's actually the glibc malloc implementation at fault vs bash not doing the right thing. -mike
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