linux-kernel - Re: [PATCH 1/1] kernel/crash_core.c - Add crashkernel=auto for x86 and ARM

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Date:   Thu, 19 Nov 2020 12:52:10 -0800
From:   Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
To:     Kairui Song <kasong@...hat.com>
Cc:     John Donnelly <john.p.donnelly@...cle.com>, stable@...r.kernel.org,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Vinod Koul <vkoul@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Anson Huang <Anson.Huang@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Michael Walle <michael@...le.cc>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Olof Johansson <olof@...om.net>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Diego Elio Pettenò <flameeyes@...meeyes.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        kexec@...ts.infradead.org, linux-doc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] kernel/crash_core.c - Add crashkernel=auto for x86
 and ARM

Hi,
[I’m resending this email as it failed to be sent to certain emails.]

> And I think crashkernel=auto could be used as an indicator that user
> want the kernel to control the crashkernel size, so some further work
> could be done to adjust the crashkernel more accordingly. eg. when
> memory encryption is enabled, increase the crashkernel value for the
> auto estimation, as it's known to consume more crashkernel memory.
> 
Thanks for the suggestion! I tried to keep it simple and leave it to the user to change Kconfig in case a different range is needed. Based on experience, these ranges work well for most of the regular cases.

> 
> But why not make it arch-independent? This crashkernel=auto idea
> should simply work with every arch.

Thanks! I’ll be making it arch-independent in the v2 patch.

> 
> I think this rounding may be better moved to the arch specified part
> where parse_crashkernel is called?

Thanks for the suggestion. Could you please elaborate why do we need to do that?

Thanks,
Saeed