Messages in this thread |  | | | Date | Sun, 14 Feb 2010 00:28:39 +0100 | | From | Stefan Richter <> | | Subject | Re: [kernel.org users] XZ Migration discussion |
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Jean Delvare wrote: > For my testing, I have been using the slowest machine I still have > available here: a Pentium 166 MMX, with 64 MB of memory and a slow hard > disk drive. I've been writing down the duration of each task it took to > boot kernel 2.6.27.45 on this machine. I did this for both .gz and .bz2 > formats. > > Raw results are as follow (format=min:s): > > downloading linux-2.6.27.tar.bz2 5:01 > downloading patch-2.6.27.45.bz2 0:02 > unpacking linux-2.6.27.tar.bz2 7:28 > applying patch-2.6.27.45.bz2 1:21 > ---------------------------------------------- > total for bz2 13:52 > > downloading linux-2.6.27.tar.gz 6:23 > downloading patch-2.6.27.45.gz 0:02 > unpacking linux-2.6.27.tar.gz 3:20 > applying patch-2.6.27.45.gz 1:10 > ---------------------------------------------- > total for gz 10:55 > > So the gz option is unsurprisingly faster, setting up the source tree > takes almost 3 minutes less (-21%).
If the download link had been slower than about 75 kB/s, the bz2 option would have been faster even on this old machine.
With xz, download would be faster than bz2 and decompression would be somewhere between bz2 and gz --- at least on machines without notable memory constraints. xz's decompressor is more memory hungry than bzip2's one as far as I understand their manual pages. But at the default xz compressor setting of -6, the decompressor will still use just 10 MB and should therefore not cause even your 64 MB machine to swap all the time during decompression.
> Then the (common) build and installation times: > > building 117:26 > installing modules 0:12 > ---------------------------------------------- > total 117:38 > > This is a customized kernel, as small as I could do, with almost no > features and the minimal set of drivers. As you can see, the build time > is one order of magnitude greater than the tree setup time. Comparing > the total times from download to install between bz2 and gz: > > bz2: 13:52 + 117:38 = 131:30 > gz: 10:55 + 117:38 = 128:33 > > Compared to bz2, gz saves... 2% on the overall time. As a conclusion, I > think we can plain discard the argument "I need .gz because my machine > is slow" from now on. It simply doesn't hold.
Yep, whether the target machine is meant to compile the kernel or to be used to browse the source code (with a bare minimum of comfort), the hardware resources required for either task mean that there isn't such a great difference between gz, bz2, xz WRT resource requirements at the receivers, except that xz goes easiest on network bandwidth and disk utilization. -- Stefan Richter -=====-==-=- --=- -==-= http://arcgraph.de/sr/
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