makedumpfile 1.5.4, 734G kdump tests

Cliff Wickman
2013-07-09T16:24:29Z

I have run some tests with the latest makedumpfile and kexec and the
results (below) look very good to me.

This particular test machine has a megaraid root, which had been a problem
with previous kexec-tools (I did have to allocate a lot of low memory).

My 3.10 kernel does have Hatayama's vmcore mmap patches.

My only remaining concern for makedumpfile is the filtering of huge pages.
I believe that patch is in progress; but I don't see it in 1.5.4.

-Cliff

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.
- The vmcore mmap kernel patch cuts off about 1/3 of both page scan time and
data copy time.
I hope those patches reach Linus' tree shortly, as you expect.
- Data copy time is dominated by compression time; writing compressed data
to /dev/null uses almost the same time as writing to disk.
I hope your efforts to multi-thread the crash kernel go forward.

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