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

[Petr Tesarik]

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?

Petr T