bug#18892: few test failure with 'grep-2.20.72-d512'

[Bruce Dubbs]

Jim Meyering wrote:
> Your total free memory is obviously larger than 2GiB, but remember
> that what's listed there is the total, while the offending usage
> required a *contiguous* 2GiB region.

My understanding of the kernel is that it allocates in 4K blocks and 
maps them to user space to appear to be contiguous.

If I write a program that does:
  size_t size = 0xA0000000;  // 2,684,354,560
  char*  mem  = (char*) malloc( size );
  size_t i;

  for ( i = 0; i < size; i++, mem++ ) *mem='A';

There are no problems, but it does take about 9 seconds on my system.
The start address is 7ffa5405d010.
The end   address is 7ffaf405d010.

What am I missing?

  -- Bruce


> On Sat, Nov 1, 2014 at 7:56 PM, Bruce Dubbs <address@hidden> wrote:
> > Jim Meyering wrote:
> > > On Wed, Oct 29, 2014 at 2:56 PM, Bruce Dubbs <address@hidden>
> > > wrote:
> > > ...
> > > > > >      http://meyering.net/grep/grep-2.20.72-d512.tar.xz
> > >
> > > ...
> > > > Linux From Scratch 7.6
> > > >
> > > > configure and make were clean.
> > > >
> > > > $ env RUN_EXPENSIVE_TESTS=yes make -k check
> > > >
> > > > big-match: skipped test: not enough main memory to run the test
> > > > sjis-mb: skipped test: SJIS locale not found
> > > >
> > > > I do have 8G of memory.
> > >
> > >
> > > That test fails when grep fails to allocate enough space to hold a 2GiB
> > > line.
> > > No big deal, and not hard to imaging happening with a few applications
> > > in 8GiB of RAM.
> >
> >
> > Curious though.  It should have been OK.  I did not have any gui running at
> > the time.  Even if RAM was full, swap should have handled it.
> >
> > $ free
> >              total       used       free     shared    buffers     cached
> > Mem:      8105972    2380012    5725960        880     610460     326820
> > -/+ buffers/cache:   1442732    6663240
> > Swap:    10485756       3216   10482540
> >
> >    -- Bruce