linux-kernel - Re: [PATCH v2] Add the values related to buddy system for filtering free pages.

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Message-Id: <20130208114509.0755d9012cdfbcbd99c3a4ff@mxc.nes.nec.co.jp>
Date:	Fri, 8 Feb 2013 11:45:09 +0900
From:	Atsushi Kumagai <kumagai-atsushi@....nes.nec.co.jp>
To:	lisa.mitchell@...com
Cc:	vgoyal@...hat.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	d.hatayama@...fujitsu.com, ebiederm@...ssion.com,
	akpm@...ux-foundation.org, cpw@....com
Subject: Re: [PATCH v2] Add the values related to buddy system for filtering
 free pages.

Hello Lisa,

On Thu, 07 Feb 2013 05:29:11 -0700
Lisa Mitchell <lisa.mitchell@...com> wrote:

> > > > Also, I have one question. Can we always think of 1st and 2nd kernels
> > > > are same?
> > > 
> > > Not at all.  Distros frequently implement it with the same kernel in
> > > both role but it should be possible to use an old crusty stable kernel
> > > as the 2nd kernel.
> > > 
> > > > If I understand correctly, kexec/kdump can use the 2nd kernel different
> > > > from the 1st's. So, differnet kernels need to do the same thing as makedumpfile
> > > > does. If assuming two are same, problem is mush simplified.
> > > 
> > > As a developer it becomes attractive to use a known stable kernel to
> > > capture the crash dump even as I experiment with a brand new kernel.
> > 
> > To allow to use the 2nd kernel different from the 1st's, I think we have
> > to take care of each kernel version with the logic included in makedumpfile
> > for them. That's to say, makedumpfile goes on as before.
> > 
> > 
> > Thanks
> > Atsushi Kumagai
> 
> 
> Atsushi and Vivek:  
> 
> I'm trying to get the status of whether the patch submitted in
> https://lkml.org/lkml/2012/11/21/90  is going to be accepted upstream
> and get in some version of the Linux 3.8 kernel.   I'm replying to the
> last email thread above on kexec_lists and lkml.org  that I could find
> about this patch.  
> 
> I was counting on this kernel patch to improve performance of
> makedumpfilev1.5.1, so at least it wouldn't be a regression in
> performance over makedumpfile v1.4.   It was listed as recommended in
> the makedumpfilev1.5.1 release posting:
> http://lists.infradead.org/pipermail/kexec/2012-December/007460.html
> 
> 
> All the conversations in the thread since this patch was committed seem
> to voice some reservations now, and reference other fixes being tried to
> improve performance.
> 
> Does that mean you are abandoning getting this patch accepted upstream,
> in favor of pursuing other alternatives?

No, this patch has been merged into -next, we should just wait for it to be
merged into linus tree.

  http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=commit;h=0c63e90dd1c7b35ae2ea9475ba67cf68d8801a26

What interests us now is improvement for interfaces of /proc/vmcore,
it's not alternative but another idea which can be consistent with
this patch.


Thanks
Atsushi Kumagai

> 
> I had hoped this patch would be okay to get accepted upstream, and then
> other improvements could be built on top of it.  
> 
> Is that not the case?   
> 
> Or has further review concluded now that this change is a bad idea due
> to adding dependence of this new makedumpfile feature on some deep
> kernel memory internals?
> 
> Thanks,
> 
> Lisa Mitchell
> 
>
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