Re: [Crash-utility] what is recommended dump level (makedumpfile)
----- "Tokuhisa Inagaki" <tokuhisa.inagaki(a)ctc-g.co.jp> wrote:
Hi, all.
what is recommended dump level when using makedumpfile
(kdump)? I'm looking for explanation like this.
------------ from diskdump document --------------------
Note that the partial dump feature has some risks. There
are memory management lists which are scanned for a page's
memory attribute, so if the list has been corrupted, the
scanning process may fail. For example, when specifying a
dump_level from 4-7 or from 12-15, the kernel's free page
linked lists are scanned; if the list is corrupt, diskdump
may hang. Furthermore, it is possible that a page type
that has been skipped may be necessary to fully investigate
the cause of some issues. Therefore, a memory collection
level should be selected to suit each situation. The
recommended level is 19, because it is easiest to determine
whether a page is zero-filled or if it is a page cache page,
and because no page lists need to be traversed.
-------------------------------------------------------
Does anyone know document describing these things
when using makedumpfile ?
Thanks,
toku.
I don't know of any document for makedumpfile other than the
/usr/share/doc/kexec-tools-<version>/kexec-kdump-howto.txt
and the output of "makedumpfile -h". Neither of those has
any caveats such as the diskdump document above, but I'm
guessing that the same kind of issues would apply when makedumpfile
walks page lists, the mem_map, etc. But I don't know what the
failure mode would be, given that it's a user application as opposed
to a kernel module.
In any case, the makedumpfile maintainers are on this list
and hopefully can shed some light on your query.
Dave