From: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
jay.vosburgh@canonical.com, kernel@gpiccoli.net
Subject: Re: [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages creation
Date: Tue, 15 Oct 2019 01:50:07 -0300 [thread overview]
Message-ID: <92e8451a-3a64-cde9-a879-10c0c9e857aa@canonical.com> (raw)
In-Reply-To: <c145a020-5ae0-e3a5-0251-199618cfaa9e@oracle.com>
On 14/10/2019 15:25, Mike Kravetz wrote:
> [...]
> I don't know much about early_param(), so I will assume this works as you
> describe. However, a quick grep shows hugepage options for ia64 also with
> early_param.
>
Thanks a lot for the prompt and quite informative reply Mike.
I've checked this IA64 parameter after your mention, and it just sets
the hugepages size, I don't think it'll affect the purpose of this patch.
>> * The return when sysctl handler is prevented to progress due to
>> nohugepages is -EINVAL, but could be changed; I've just followed
>> present code there, but I'm OK changing that if we have suggestions.
>
> It looks like you only have short circuited/prevented nr_hugepages via
> sysfs/sysctl. Theoretically, one could set nr_overcommit_hugepages and
> still allocate hugetlb pages. So, if you REALLY want to shut things down
> you need to stop this as well.
>
> There is already a macro hugepages_supported() that can be set by arch
> specific code. I wonder how difficult it would be to 'overwrite' the
> macro if nohugepages is specified. Perhaps just a level of naming
> indirection. This would use the existing code to prevent all hugetlb usage.
>
Outstanding! It's a much better idea to use hugepages_supported()
infrastructure, it prevents even the creation of hugepages-related sysfs
entries; I've worked a V2 with this modification, and it worked fine,
thanks for the suggestion.
> It seems like there may be some discussion about 'the right' way to
> do kdump. I can't add to that discussion, but if such an option as
> nohugepages is needed, I can help.
>
I think this parameter may be important/useful not only for kdump - it
is a legitimate way of disabling hugepages, something we don't currently
have on kernel. I'll submit a V2, for Ubuntu kdump specially this is
quite helpful!
Cheers,
Guilherme
prev parent reply other threads:[~2019-10-15 4:50 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-11 22:39 [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages creation Guilherme G. Piccoli
2019-10-11 23:35 ` Qian Cai
2019-10-11 23:41 ` Guilherme Piccoli
2019-10-11 23:52 ` Qian Cai
2019-10-12 0:41 ` Guilherme Piccoli
2019-10-15 12:18 ` Michal Hocko
2019-10-15 13:58 ` Guilherme G. Piccoli
2019-10-15 14:05 ` Michal Hocko
2019-10-15 14:09 ` Guilherme G. Piccoli
2019-10-18 18:29 ` Mike Kravetz
2019-10-24 16:21 ` Guilherme G. Piccoli
2019-10-14 18:25 ` Mike Kravetz
2019-10-15 4:50 ` Guilherme G. Piccoli [this message]
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