linux-kernel - Re: [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages creation

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Message-Id: <36C2B5DF-7F21-42C6-BA77-6D86EDCB6BB3@lca.pw>
Date:   Fri, 11 Oct 2019 19:35:57 -0400
From:   Qian Cai <cai@....pw>
To:     "Guilherme G. Piccoli" <gpiccoli@...onical.com>
Cc:     linux-mm@...ck.org, mike.kravetz@...cle.com,
        linux-kernel@...r.kernel.org, jay.vosburgh@...onical.com,
        kernel@...ccoli.net
Subject: Re: [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages creation



> On Oct 11, 2019, at 6:40 PM, Guilherme G. Piccoli <gpiccoli@...onical.com> wrote:
> 
> Kdump kernels won't benefit from hugepages - in fact it's quite opposite,
> it may be the case hugepages on kdump kernel can lead to OOM if kernel
> gets unable to allocate demanded pages due to the fact the preallocated
> hugepages are consuming a lot of memory.
> 
> This patch proposes a new kernel parameter to prevent the creation of
> HugeTLB hugepages - we currently don't have a way to do that. We can
> even have kdump scripts removing the kernel command-line options to
> set hugepages, but it's not straightforward to prevent sysctl/sysfs
> configuration, given it happens in later boot or anytime when the
> system is running.

Typically, kdump kernel has its own initramfs, and don’t even need to mount a rootfs, so I can’t see how sysfs/sysctl is relevant here.