Re: A few patches to consider

Petr Tesarik
2013-09-20T20:52:56Z

On Thu, 19 Sep 2013 05:00:02 +0000
Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> wrote:

> (2013/09/19 11:13), HATAYAMA Daisuke wrote:
> > (2013/09/18 12:00), Atsushi Kumagai wrote:
> >> (2013/08/30 10:33), HATAYAMA Daisuke wrote:
> >>> (2013/08/29 7:08), Cliff Wickman wrote:
> >>>> From: Cliff Wickman <cpw@sgi.com>
> >>>>
> >>>> I am submitting 6 patches that I have found helpful in speeding the dump
> >>>> process or clarifying the progress report.
> >>>> They are not a series, and should not be interdependent. But if you
> >>>> find any dependencies I apply them in this order:
> >>>> [PATCH] makedumpfile: reverse -c and -p if using snappy compression
> >>>> [PATCH] makedumpfile: use non-cyclic when possible
> >>>> [PATCH] makedumpfile: shorten cyclic exclude-unnecessary passes
> >>>> [PATCH] makedumpfile: shorten cyclic unnecessary-page scans
> >>>> [PATCH] makedumpfile: show needed memory
> >>>> [PATCH] makedumpfile: search for a debug vmlinux
> >>>>
> >>>> The last one (search for a debug vmlinux) is useful in identifying huge
> >>>> pages with the PG_head/PG-tail flags. There was a patch from Petr Tesarik
> >>>> that enables that huge page filtering. I don't think you are taking that one
> >>>> as-is, but are reworking it. Seems like Hatayama-san was doing that work.
> >>>
> >>> No. If I have good memory, Kumagai-san was investigating how to integrate
> >>> huge page filtering into current memory types currently supported by
> >>> makedumpfile.
> >>
> >> Yes, I was investigating it but I'm not working for it now.
> >>
> >> I think main features should work without vmlinux,
> >> but it was impossible about his patch as said by himself:
> >>
> >>> This patch depends on exporting the relevant PG_* flags from the
> >>> kernel (in VMCOREINFO), and that's where I got stuck, because depending
> >>> on the number of available bits for the page flags, the kernel either
> >>> has PG_head and PG_tail, or only PG_compound, so I needed a #ifdef, and
> >>> the kernel maintainers didn't like the conditional.
> >>> I can restart the discussion with kernel maintainers and see what I can do
> >>
> >> Therefore, I waited that his work is finished and I was going to continue
> >> my work, but I didn't say my thinking definitely, sorry.
> >>
> >> Anyway, I should cooperate with Petr to develop huge page filtering,
> >> so could you let me know the status of your work ?
> >>
> >
> > To whom do you make this question? It seems Cliff according to content of this question.
> > If so you should resend. If to me, I have not done huge page filtering work at all so far
> > as I already said in the previous mail in this thread.
>
> Sorry for confusing you, I asked Petr.
> According to Cliff's 1st mail:
>
> > From: Cliff Wickman <cpw@sgi.com>
> >
> > This fix comes from Petr Tesarik <ptesarik@suse.cz>, and was applied
> > to the SuSE version of makedumpfile.
> > I don't see it in the mmap version.
> > It is important to filtering out a great deal of user memory.
> >
> > But this from Petr on 5/15:
> >> This patch depends on exporting the relevant PG_* flags from the
> >> kernel (in VMCOREINFO), and that's where I got stuck, because depending
> >> on the number of available bits for the page flags, the kernel either
> >> has PG_head and PG_tail, or only PG_compound, so I needed a #ifdef, and
> >> the kernel maintainers didn't like the conditional.
> >> I can restart the discussion with kernel maintainers and see what I can do
> > So I'm not sending to the kexec list until he's ready.
>
> I understood Petr tried to add PG_* flags into VMCOREINFO,
> but it seems not completed in linux-next at this time.
> To prepare the flags is important to huge page filtering,
> I want to know the status of Petr's work.

This got blocked when the maintainer of that subsystem didn't answer me
what he considered a clean solution. And then it got sidetracked by
other issues. I can resume from there, because I also need these flags
properly exported in VMCOREINFO.

OK, time to ask again.

Petr T