[RFC PATCH 2/4] makedumpfile: Add partial bitmap for cyclic.

[Atsushi Kumagai]

Hello HATAYAMA-san,

On Mon, 04 Jun 2012 12:19:57 +0900 (JST)
HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> wrote:

> > + */
> > +#define BUFSIZE_CYCLIC	        (8192)
> > +#define PFN_CYCLIC		(BUFSIZE_CYCLIC * BITPERBYTE)
> > +
> > +
> > +/*
> >   * Minimam vmcore has 2 ProgramHeaderTables(PT_NOTE and PT_LOAD).
> 
> How did you choose this buffer size? Best performance? I think the
> performacne varies according to this buffer size, and to evaluate it,
> it's useful to be able to specify the size through command-line.

Honestly, the buffer size has no means, I defined it without a specific reason
at first.

However, it's understandable that the size is important key for performance and
I agree with your opinion that enabling to specify the size is useful.

But, I noticed just now, prototype with increased buffer size isn't work correctly.

 - BUFSIZE_CYCLIC = 8192:

    $ makedumpfile -Kcd31 vmcore testdump.Kcd31
    ...
    The dumpfile is saved to testdump.Kcd31.

    makedumpfile Completed.
    $ ls -l testdump.*
    -rw------- 1 kumagai kumagai 21167309  6月  7 13:55 testdump.Kcd31
    -rw------- 1 kumagai kumagai 21167309  6月  7 13:28 testdump.cd31
    $

 - BUFSIZE_CYCLIC = 16384:

    $ makedumpfile -Kcd31 vmcore testdump.Kcd31
    ...
    The dumpfile is saved to testdump.Kcd31.

    makedumpfile Completed.
    $ ls -l testdump.*
    -rw------- 1 kumagai kumagai 18836948  6月  7 13:59 testdump.Kcd31
    -rw------- 1 kumagai kumagai 21167309  6月  7 13:28 testdump.cd31
    $


I must review my code quickly.


Thanks
Atsushi Kumagai