Re: makedumpfile 1.5.4, 734G kdump tests

[Cliff Wickman <cpw@sgi.com>]

On Thu, Jul 11, 2013 at 09:06:47AM -0400, Vivek Goyal wrote:
> On Tue, Jul 09, 2013 at 11:24:03AM -0500, Cliff Wickman wrote:
> 
> [..]
> > UV2000   memory: 734G
> > makedumpfile: makedumpfile-1.5.4
> > kexec:   git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
> > booted with   crashkernel=1G,high crashkernel=192M,low
> > non-cyclic mode
> > 
> > write to       option            init&scan sec.   copy sec.  dump size
> > -------------  -----------------           ----   ---------  ---------
> > megaraid disk  no compression                19          91      11.7G
> > megaraid disk  zlib compression              20         209       1.4G
> > megaraid disk  snappy compression            20          46       2.4G
> > megaraid disk  snappy compression no mmap    30          72       2.4G
> > /dev/null      no compression                19          28          -
> > /dev/null      zlib compression              19         206          -
> > /dev/null      snappy compression            19          41          -
> > 
> > Notes and observations
> > - Snappy compression is a big win over zlib compression; over 4 times faster
> >   with a cost of relatively little disk space.
> 
> Thanks for the results Cliff. If it is not too much of trouble, can you
> please also test with lzo compression on same configuration. I am 
> curious to know how much better snappy performs as compared to lzo.
> 
> Thanks
> Vivek

Ok.  I repeated the tests and included LZO compression.

UV2000   memory: 734G
makedumpfile: makedumpfile-1.5.4     non-cyclic mode
kexec: git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
3.10 kernel with vmcore mmap patches
booted with   crashkernel=1G,high crashkernel=192M,low

write to       compression       init&scan sec.   copy sec.  dump size
-------------  -----------------           ----   ---------  ---------
megaraid disk  no compression                20          86      11.6G
megaraid disk  zlib compression              19         209       1.4G
megaraid disk  snappy compression            20          47       2.4G
megaraid disk  lzo compression               19          54       2.8G

/dev/null      no compression                19          28          -
/dev/null      zlib compression              20         206          -
/dev/null      snappy compression            19          42          -
/dev/null      lzo compression               20          47          -

Notes:
- Snappy compression is still be fastest (and more compressed than LZO),
  but LZO is close.
- Compression and I/O seem pretty well overlapped, so I am not sure that
  multithreading the crash kernel (to speed compression) will speed the
  dump as much I was hoping, unless perhaps the I/O device is an SSD.

-Cliff
-- 
Cliff Wickman
SGI
cpw@sgi.com
(651) 683-3824

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