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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rfn1D-00000008x3a-1Duu; Thu, 29 Feb 2024 20:28:39 +0000 Date: Thu, 29 Feb 2024 20:28:39 +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-Rspamd-Queue-Id: 20EA91A0013 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 8ti6fhkrha665y4g69gj9u3r8qc9giha X-HE-Tag: 1709238523-84409 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On Thu, Feb 29, 2024 at 11:34:33AM -0700, Yu Zhao wrote: > Compared with the hugeTLB pool approach, THP zones tap into core MM > features including: > 1. THP allocations can fall back to the lower zones, which can have > higher latency but still succeed. > 2. THPs can be either shattered (see Chapter Two) if partially > unmapped or reclaimed if becoming cold. > 3. THP orders can be much smaller than the PMD/PUD orders, e.g., 64KB > contiguous PTEs on arm64 [1], which are more suitable for client > workloads. Can this mechanism be used to fully replace the hugetlb pool approach? That would be a major selling point. It kind of feels like it should, but I am insufficiently expert to be certain. I'll read over the patches sometime soon. There's a lot to go through. Something I didn't see in the cover letter or commit messages was any discussion of page->flags and how many bits we use for ZONE (particularly on 32-bit). Perhaps I'll discover the answer to that as I read.