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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rhA6Q-00000001l3a-1lb4; Mon, 04 Mar 2024 15:19:42 +0000 Date: Mon, 4 Mar 2024 15:19:42 +0000 From: Matthew Wilcox To: Yu Zhao Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, Jonathan Corbet Subject: Re: [Chapter One] THP zones: the use cases of policy zones Message-ID: References: <20240229183436.4110845-1-yuzhao@google.com> <20240229183436.4110845-2-yuzhao@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240229183436.4110845-2-yuzhao@google.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4FE3940025 X-Stat-Signature: depe11edgnn1ebfcrjzxsugnf6ndi875 X-HE-Tag: 1709565590-547080 X-HE-Meta: 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 S4p4BPpL uIxntn9umLdeKHiL4FeZSwmNENScFH+nLcVAwehsq0aFrkgy/WiUiJIpMEpEz4cbpjTrn4a+p+IgcG/05m5cs7AzlXz+Ey0DEXpuAxwvqlaWdRLdyth9VC5RJlRlOVlGLPAJSpekSTNhXbFcfijYcutz20M/diLwlWmWaMFTjoCxnQpI6wmmxDBMRJse/PRSajSH6 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000105, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Feb 29, 2024 at 11:34:33AM -0700, Yu Zhao wrote: > ZONE_MOVABLE becomes the first policy zone, followed by two new policy > zones: > 1. ZONE_NOSPLIT, which contains pages that are movable (inherited from > ZONE_MOVABLE) and restricted to a minimum order to be > anti-fragmentation. The latter means that they cannot be split down > below that order, while they are free or in use. > 2. ZONE_NOMERGE, which contains pages that are movable and restricted > to an exact order. The latter means that not only is split > prohibited (inherited from ZONE_NOSPLIT) but also merge (see the > reason in Chapter Three), while they are free or in use. These two zones end up solving a problem for memdescs. So I'm in favour! I added Option 5 to https://kernelnewbies.org/MatthewWilcox/BuddyAllocator I think this patch needs to be split into more digestable chunks, but a quick skim of it didn't reveal anything egregiously wrong. I do still have that question about the number of bits used for Zone in page->flags. Probably this all needs to be dependent on CONFIG_64BIT?