linux-kernel - Re: [PATCH V3] KSM: allow dedup all tasks memory

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Message-ID: <d43da6ad1a3c164aa03e0f22f065591a@natalenko.name>
Date:   Tue, 13 Nov 2018 15:23:50 +0100
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     jannh@...gle.com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, timofey.titovets@...esis.ru,
        willy@...radead.org
Subject: Re: [PATCH V3] KSM: allow dedup all tasks memory

Hi.

> Yep. However, so far, it requires an application to explicitly opt in
> to this behavior, so it's not all that bad. Your patch would remove
> the requirement for application opt-in, which, in my opinion, makes
> this way worse and reduces the number of applications for which this
> is acceptable.

The default is to maintain the old behaviour, so unless the explicit 
decision is made by the administrator, no extra risk is imposed.

> As far as I know, basically nobody is using KSM at this point. There
> are blog posts from several cloud providers about these security risks
> that explicitly state that they're not using memory deduplication.

I tend to disagree here. Based on both what my company does and what 
UKSM users do, memory dedup is a desired option (note "option" word 
here, not the default choice).

Thanks.

-- 
   Oleksandr Natalenko (post-factum)