linux-kernel - Re: [PATCH 2/2] dmabuf/heaps: implement DMA_BUF_IOCTL_RW_FILE for system

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Message-ID: <2487bad4-81d6-4ea2-96a7-a6ac741c9d9c@amd.com>
Date: Thu, 15 May 2025 16:26:08 +0200
From: Christian König <christian.koenig@....com>
To: wangtao <tao.wangtao@...or.com>,
 "sumit.semwal@...aro.org" <sumit.semwal@...aro.org>,
 "benjamin.gaignard@...labora.com" <benjamin.gaignard@...labora.com>,
 "Brian.Starkey@....com" <Brian.Starkey@....com>,
 "jstultz@...gle.com" <jstultz@...gle.com>,
 "tjmercier@...gle.com" <tjmercier@...gle.com>
Cc: "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "wangbintian(BintianWang)" <bintian.wang@...or.com>,
 yipengxiang <yipengxiang@...or.com>, liulu 00013167 <liulu.liu@...or.com>,
 hanfeng 00012985 <feng.han@...or.com>
Subject: Re: [PATCH 2/2] dmabuf/heaps: implement DMA_BUF_IOCTL_RW_FILE for
 system_heap

On 5/15/25 16:03, wangtao wrote:
> [wangtao] My Test Configuration (CPU 1GHz, 5-test average):
> Allocation: 32x32MB buffer creation
> - dmabuf 53ms vs. udmabuf 694ms (10X slower)
> - Note: shmem shows excessive allocation time

Yeah, that is something already noted by others as well. But that is orthogonal.

> 
> Read 1024MB File:
> - dmabuf direct 326ms vs. udmabuf direct 461ms (40% slower)
> - Note: pin_user_pages_fast consumes majority CPU cycles
> 
> Key function call timing: See details below. 

Those aren't valid, you are comparing different functionalities here.

Please try using udmabuf with sendfile() as confirmed to be working by T.J.

Regards,
Christian.