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Peter Anvin" , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210309174113.5597-1-osalvador@suse.de> <20210309174113.5597-4-osalvador@suse.de> <3471fe0e-d8f4-c8fe-2096-8d9c8b1ab5bc@redhat.com> <20210310174953.GA16289@linux> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v5 3/4] x86/vmemmap: Handle unpopulated sub-pmd ranges Message-ID: <1814c21c-b822-0ec6-c16d-92424d00663a@redhat.com> Date: Wed, 10 Mar 2021 18:58:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210310174953.GA16289@linux> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Stat-Signature: tb8et659mapdgfu6sq5k8ept1feorc4d X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8A850E000127 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615399114-437712 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10.03.21 18:49, Oscar Salvador wrote: > On Tue, Mar 09, 2021 at 06:52:38PM +0100, David Hildenbrand wrote: >>> -#define PAGE_INUSE 0xFD >>> +#ifdef CONFIG_SPARSEMEM_VMEMMAP >>> +#define PAGE_UNUSED 0xFD >>> + >>> +/* Returns true if the PMD is completely unused and thus it can be f= reed */ >>> +static bool __meminit vmemmap_pmd_is_unused(unsigned long addr, unsi= gned long end) >>> +{ >> >> I don't think the new name is any better. It implies that all it does = is a >> check - yet it actually clears the given range. (I prefer the old name= , but >> well, I came up with that, so what do I know :D ) >=20 > Sorry, I did not mean to offend here. Oh, I didn't feel offended - I was rather expressing that my opinion=20 might be biased because I came up with these names in the s390x variant ;= ) >=20 > Something like: vmemmap_is_pmd_unused_after_clearing_it would be a bit = better > I guess. > Tbh, both this and previous one looked fine to me, but I understand whe= re Dave > confusion was coming from, that is why I decided to rename it. >=20 > Maybe a middle-ground would have been to expand the comment above. Thinking again, I guess it might be a good idea to factor out the core=20 functions into common code. For the optimization part, it might make=20 sense too pass some "state" structure that contains e.g.,=20 "unused_pmd_start". Then we don't have diverging implementations of essentially the same thin= g. Of course, we can do that on top of this series - unifying both=20 implementations. --=20 Thanks, David / dhildenb