linux-kernel - Re: Selecting MMU page size for an architecture

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Message-ID: <CACCGGCfQp7W3dCPNDh9sWTBCpC-adFwhhDaoHhwx8dyXa3UBeA@mail.gmail.com>
Date:   Sun, 23 Jan 2022 21:05:24 -0500
From:   Jon Masters <jcm@...masters.org>
To:     Sergey Organov <sorganov@...il.com>
Cc:     lkml <linux-kernel@...r.kernel.org>
Subject: Re: Selecting MMU page size for an architecture

Hey Sergey,

On Thu, Dec 23, 2021 at 8:15 AM Sergey Organov <sorganov@...il.com> wrote:

> We are building custom CPU and have an option to choose either 4K or 16K
> MMU minimum page size that will then be fixed in the hardware. For
> reasons unrelated to the Linux kernel we'd prefer 16K, but I have some
> doubts.
>
> What pros and cons for kernel and user-space operation 16K pages will
> have over more usual 4K pages? Anything we should worry about?

If you want maximum compatibility with existing source written for
industry at large (e.g. x86/Arm) and even the assumptions in other
devices (and their firmware) you might connect (PCI, or even on-SoC)
then you'll want to go with 4K. However, if I were designing a brand
new architecture today and didn't care about legacy, I would
definitely consider following Apple into 16K.

Jon.

-- 
Computer Architect