[PATCH] makedumpfile: change the wrong code to calculate bufsize_cyclic for elf dump

[Vivek Goyal]

On Mon, Apr 21, 2014 at 05:46:30PM +0200, Petr Tesarik wrote:
> On Mon, 21 Apr 2014 11:19:14 -0400
> Vivek Goyal <vgoyal at redhat.com> wrote:
> 
> > On Fri, Apr 18, 2014 at 09:41:33PM +0200, Petr Tesarik wrote:
> > > On Fri, 18 Apr 2014 22:29:12 +0800
> > > "bhe at redhat.com" <bhe at redhat.com> wrote:
> >[...]
> > > > Instead, I am wondering how the 80% comes from, and why 20% of free
> > > > memory must be safe.
> > > 
> > > I believe these 80% come from the default value of vm.dirty_ratio,
> > 
> > Actually I had suggested this 80% number when --cyclic feature was
> > implemented. And I did not base it on dirty_ratio. Just a random
> > suggestion.
> 
> Hm. OK, you seem to have very good suggestions, even if they are
> random. ;-)
> 
> > > which is 20%. In other words, the kernel won't block further writes
> > > until 20% of available RAM is used up by dirty cache. But if you
> > > fill up all free memory with dirty pages and then touch another (though
> > > allocated) page, the kernel will go into direct reclaim, and if nothing
> > > can be written out ATM, it will invoke the OOM Killer.
> > 
> > We can start playig with reducing dirty_raio too and see how does it go.
> 
> Or use direct I/O... Is it still broken?

May be if that turns out to be an issue. Or just reduce dirty_ratio to say
5 instead of default 20. Different things can be tried once we know what's
the root cause of the issue.

Thanks
Vivek