linux-kernel - Re: [PATCHv1, RFC 0/8] Boot-time switching between 4- and 5-level paging

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Message-ID: <20170526133504.GD24144@tassilo.jf.intel.com>
Date:   Fri, 26 May 2017 06:35:04 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv1, RFC 0/8] Boot-time switching between 4- and 5-level
 paging

> Even ignoring all of above, I don't see much benefit of having per-mm
> switching. It adds complexity without much benefit -- saving few lines of
> logic during early boot doesn't look as huge win to me.

Also giving kthreads a different VM would prevent lazy VM switching
when switching from/to idle, which can be quite important for performance
when doing fast IO.

-Andi