linux-kernel - Re: [PATCH] vduse: Use fixed 4KB bounce pages for arm64 64KB page size

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Message-ID: <CACGkMEvWNOjFU0pgiS=LF2B+yEC-y_RU3w_P5_dr10RPH+5xrg@mail.gmail.com>
Date: Mon, 15 Sep 2025 16:21:57 +0800
From: Jason Wang <jasowang@...hat.com>
To: sheng.zhao@...edance.com
Cc: mst@...hat.com, xuanzhuo@...ux.alibaba.com, eperezma@...hat.com, 
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	xieyongji@...edance.com
Subject: Re: [PATCH] vduse: Use fixed 4KB bounce pages for arm64 64KB page size

On Mon, Sep 15, 2025 at 3:34 PM <sheng.zhao@...edance.com> wrote:
>
> From: Sheng Zhao <sheng.zhao@...edance.com>
>
> The allocation granularity of bounce pages is PAGE_SIZE. This may cause
> even small IO requests to occupy an entire bounce page exclusively.

This sounds more like an issue of the IOVA allocating that use the
wrong granular?

> The
> kind of memory waste will be more significant on arm64 with 64KB pages.
>
> So, optimize it by using fixed 4KB bounce pages.
>
> Signed-off-by: Sheng Zhao <sheng.zhao@...edance.com>

Thanks