linux-kernel - Re: [PATCH 2/2] driver: dma-buf: use alloc_pages_bulk

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Message-ID: <CAGWkznFG2_WGmLRmHnjV-49iTX0mrt9jxQBzZYK=K9U7eKJD0g@mail.gmail.com>
Date: Wed, 15 Oct 2025 13:52:57 +0800
From: Zhaoyang Huang <huangzhaoyang@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Christian König <christian.koenig@....com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Petr Tesarik <ptesarik@...e.com>, 
	"zhaoyang.huang" <zhaoyang.huang@...soc.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	David Hildenbrand <david@...hat.com>, Mel Gorman <mgorman@...hsingularity.net>, 
	Vlastimil Babka <vbabka@...e.cz>, Sumit Semwal <sumit.semwal@...aro.org>, 
	Benjamin Gaignard <benjamin.gaignard@...labora.com>, Brian Starkey <Brian.Starkey@....com>, 
	John Stultz <jstultz@...gle.com>, "T . J . Mercier" <tjmercier@...gle.com>, linux-media@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, steve.kang@...soc.com
Subject: Re: [PATCH 2/2] driver: dma-buf: use alloc_pages_bulk_list for
 order-0 allocation

On Wed, Oct 15, 2025 at 11:21 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Wed, Oct 15, 2025 at 09:12:07AM +0800, Zhaoyang Huang wrote:
> > > Could be that we need to make this behavior conditional, but somebody would need to come up with some really good arguments to justify the complexity.
> > ok, should we use CONFIG_DMA_BUF_BULK_ALLOCATION or a variable
> > controlled by sysfs interface?
>
> No.  Explain what you're trying to solve, because you haven't yet.
Dma-buf works as a memory allocation backend could loop thousands of
times alloc_pages for allocating order-0 pages to fulfill the dozens
MB demand, this commit would like to replace the loop by once
alloc_pages_bulk. Whereas, alloc_pages_bulk_array perhaps introduces
extra memory allocation along with direct-reclaim which could be more
expensive than iterating the list. so call back the API
alloc_pages_bulk_list as well