[PATCH 1/2 V2] raw i/o and root device to use less memory

[Michael Holzheu]

On Mon, 13 Jan 2014 07:30:33 -0600
Cliff Wickman <cpw at sgi.com> wrote:

> On Mon, Jan 13, 2014 at 10:58:31AM +0100, Michael Holzheu wrote:
> > On Fri, 10 Jan 2014 11:58:30 -0600
> > Cliff Wickman <cpw at sgi.com> wrote:
> > 
> > [snip]
> > 
> > > Use O_DIRECT (raw) i/o for the dump and for the bitmaps file, so that writing
> > > to those files does not allocate kernel memory for page cache.
> > 
> > Hello Cliff,
> > 
> > Have you tested O_DIRECT together with the new vmcore mmap interface?
> > IIRC when we tried O_DIRECT together with mmap for some reason it did
> > not work.
> > 
> > Michael
> 
> Hi Michael,
> 
>   How new of a kernel do I need?  i.e. how 'new' of an mmap interface?
>   The latest kernel I used was 3.0.93 (sle11sp3).
>   And makedumpfile was 1.5.5.

I think sles11 SP3 does not support mmap for /proc/vmcore. Upstream you
need at least kernel 3.11. For makedumpfile version 1.5.5 should be ok.

Michael