Hello Hatayama-san, Thank you for your work. > Performance Comparison: > > Sample Data > > Ideally, I must have measured the performance for many enough > vmcores generated from machines that was actually running, but now > I don't have enough sample vmcores, I couldn't do so. So this > comparison doesn't answer question on I/O time improvement. This > is TODO for now. I'll measure the performance for actual vmcores by makedumpfile. Please wait for a while. Thanks. KUMAGAI, Atsushi > > Instead, I choosed worst and best cases regarding compression > ratio and speed only. Specifically, the former is /dev/urandom and > the latter is /dev/zero. > > I get the sample data of 10MB, 100MB and 1GB by doing like this: > > $ dd bs=4096 count=$((1024*1024*1024/4096)) if=/dev/urandom of=urandom.1GB > > How to measure > > Then I performed compression for each block, 4096 bytes, and > measured total compression time and output size. See attached > mycompress.c. > > Result > > See attached file result.txt. > > Discussion > > For both kinds of data, lzo's compression was considerably quicker > than zlib's. Compression ratio is about 37% for urandom data, and > about 8.5% for zero data. Actual situation of physical memory > would be in between the two cases, and so I guess average > compression time ratio is between 37% and 8.5%. > > Although beyond the topic of this patch set, we can estimate worst > compression time on more data size since compression is performed > block size wise and the compression time increases > linearly. Estimated worst time on 2TB memory is about 15 hours for > lzo and about 40 hours for zlib. In this case, compressed data > size is larger than the original, so they are really not used, > compression time is fully meaningless. I think compression must be > done in parallel, and I'll post such patch later. > > Diffstat > > * makedumpfile > > diskdump_mod.h | 3 +- > makedumpfile.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++------ > makedumpfile.h | 12 +++++++ > 3 files changed, 101 insertions(+), 12 deletions(-) > > * crash > > defs.h | 1 + > diskdump.c | 20 +++++++++++++++++++- > diskdump.h | 3 ++- > 3 files changed, 22 insertions(+), 2 deletions(-) > > TODO > > * evaluation including I/O time using actual vmcores > > Thanks. > HATAYAMA, Daisuke
