From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Baoquan He <bhe@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>, Mike Rapoport <rppt@kernel.org>
Subject: Re: [PATCH -next] mm: page_alloc: simplify has_managed_dma()
Date: Tue, 30 May 2023 14:40:14 +0800 [thread overview]
Message-ID: <0a4221cf-3703-27ff-fbdc-d7c419c5020c@huawei.com> (raw)
In-Reply-To: <ZHV5JCINq6fc/SG9@MiWiFi-R3L-srv>
On 2023/5/30 12:18, Baoquan He wrote:
> On 05/30/23 at 10:10am, Kefeng Wang wrote:
>>
>>
>> On 2023/5/29 22:26, Matthew Wilcox wrote:
>>> On Mon, May 29, 2023 at 10:40:22PM +0800, Kefeng Wang wrote:
>>>> The ZONE_DMA should only exists on Node 0, only check NODE_DATA(0)
>>>> is enough, so simplify has_managed_dma() and make it inline.
>>>
>>> That's true on x86, but is it true on all architectures?
>>
>> There is no document about numa node info for the DMA_ZONE, + Mike
>>
>> I used 'git grep -w ZONE_DMA arch/'
>
> willy is right. max_zone_pfn can only limit the range of zone, but
> can't decide which zone is put on which node. The memory layout is
> decided by firmware. I searched commit log to get below commit which
> can give a good example.
>
> commit c1d0da83358a2316d9be7f229f26126dbaa07468
> Author: Laurent Dufour <ldufour@linux.ibm.com>
> Date: Fri Sep 25 21:19:28 2020 -0700
>
> mm: replace memmap_context by meminit_context
>
> Patch series "mm: fix memory to node bad links in sysfs", v3.
>
> Sometimes, firmware may expose interleaved memory layout like this:
>
> Early memory node ranges
> node 1: [mem 0x0000000000000000-0x000000011fffffff]
> node 2: [mem 0x0000000120000000-0x000000014fffffff]
> node 1: [mem 0x0000000150000000-0x00000001ffffffff]
> node 0: [mem 0x0000000200000000-0x000000048fffffff]
> node 2: [mem 0x0000000490000000-0x00000007ffffffff]
Oh, it looks strange, but it do occur if firmware report as this way.
Thanks Willy and Baoquan, please ignore the patch.
prev parent reply other threads:[~2023-05-30 6:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-29 14:40 [PATCH -next] mm: page_alloc: simplify has_managed_dma() Kefeng Wang
2023-05-29 14:26 ` Matthew Wilcox
2023-05-30 2:10 ` Kefeng Wang
2023-05-30 4:18 ` Baoquan He
2023-05-30 6:40 ` Kefeng Wang [this message]
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