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

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Message-ID: <CACGkMEvXH+VpA-2sJ39QL4Rb3Gg0VCOKn5BApRpft=583Qcp2g@mail.gmail.com>
Date: Tue, 16 Sep 2025 15:34:52 +0800
From: Jason Wang <jasowang@...hat.com>
To: Sheng Zhao <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: [External] Re: [PATCH] vduse: Use fixed 4KB bounce pages for
 arm64 64KB page size

On Mon, Sep 15, 2025 at 7:07 PM Sheng Zhao <sheng.zhao@...edance.com> wrote:
>
>
>
> 在 2025/9/15 16:21, Jason Wang 写道:
> > 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?
> >
>
> Sorry, the previous email has a slight formatting issue.
>
> The granularity of the IOVA allocator is customized during the
> initialization of the vduse domain, and this value is also modified in
> this commit.

Ok, let's add this to the changelog.

Btw, do you have perf numbers to demonstrate the benefit?

Thanks

>
> Thanks
>
> >> 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
> >
>