linux-kernel - Re: [PATCH v2 1/2] kexec: Introduce "/sys/kernel/kexec_crash_low_size"

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Message-ID: <20160824082031.GA13889@dhcp-128-65.nay.redhat.com>
Date:   Wed, 24 Aug 2016 16:20:31 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Yinghai Lu <yinghai@...nel.org>
Cc:     Baoquan He <bhe@...hat.com>, Xunlei Pang <xlpang@...hat.com>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH v2 1/2] kexec: Introduce
 "/sys/kernel/kexec_crash_low_size"

On 08/23/16 at 06:11pm, Yinghai Lu wrote:
> On Wed, Aug 17, 2016 at 1:20 AM, Dave Young <dyoung@...hat.com> wrote:
> > On 08/17/16 at 09:50am, Xunlei Pang wrote:
> >> "/sys/kernel/kexec_crash_size" only handles crashk_res, it
> >> is fine in most cases, but sometimes we have crashk_low_res.
> >> For example, when "crashkernel=size[KMG],high" combined with
> >> "crashkernel=size[KMG],low" is used for 64-bit x86.
> >>
> >> Like crashk_res, we introduce the corresponding sysfs file
> >> "/sys/kernel/kexec_crash_low_size" for crashk_low_res.
> >>
> >> So, the exact total reserved memory is the sum of the two.
> >>
> >> crashk_low_res can also be shrunk via this new interface,
> >> and users should be aware of what they are doing.
> ...
> >> @@ -218,6 +238,7 @@ static struct attribute * kernel_attrs[] = {
> >>  #ifdef CONFIG_KEXEC_CORE
> >>       &kexec_loaded_attr.attr,
> >>       &kexec_crash_loaded_attr.attr,
> >> +     &kexec_crash_low_size_attr.attr,
> >>       &kexec_crash_size_attr.attr,
> >>       &vmcoreinfo_attr.attr,
> >>  #endif
> 
> would be better if you can use attribute_group .is_visible to control showing of
> crash_low_size only when the crash_base is above 4G.

I have same feeling that it looks odd to show low in sysfs in case no
crashkernel=,high being used. Even if crashkernel=,high is used only in
x86 the resource crashk_low is in common code. What do you think to move
it to x86?

Thanks
Dave

> 
> Thanks
> 
> Yinghai
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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