"I. Szczesniak" <iszczesniak at gmail.com> wrote:
> On 8/12/09, Alan Hargreaves <Alan.Hargreaves at sun.com> wrote:
> > It's not completely clear to me from the notes whether or not to uncompress
> > a vmdump.N needs to be done on the machine that generated the vmdump.N, or
> > if it can be done anywhere else. From a support perspective, the latter
> > would be nice. i.e. Customer uploads a vmcore.N to us and we uncompress it.
>
> Storing the file as compressed data is not as easy as you think. You
> will need a specialized unpack command as the stock version of
> /usr/bin/bunzip does not handle sparse files, vmdump.N is sparse and
> mdb will no longer be able to access the files via mmap(2).
There us bunzip2 or gunzip, which rogran are you talking about?
bzip2 compresses null bytes in an efficient way and it would not be hard
to add support for doing a lseek() instead of a write if a block of
uncompressed data appears to contain only nulls.
BTW: this is the approach I used as the first attempt to support sparse files
with star 16 years ago (see option -force-hole).
J?rg
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