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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-454913049ecsm32654384f8f.19.2026.05.12.08.46.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 08:46:51 -0700 (PDT) Date: Tue, 12 May 2026 11:46:46 -0400 From: "Michael S. Tsirkin" To: Gregory Price Cc: linux-kernel@vger.kernel.org, "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: Re: [PATCH resend v6 17/30] mm: page_alloc: propagate PageReported flag across buddy splits Message-ID: <20260512114352-mutt-send-email-mst@kernel.org> References: <6d98a35c94fa44b550afa66923c620511e2826f0.1778489843.git.mst@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, May 12, 2026 at 11:40:08AM -0400, Gregory Price wrote: > On Mon, May 11, 2026 at 05:03:19AM -0400, Michael S. Tsirkin wrote: > > When a reported free page is split via expand() to satisfy a > > smaller allocation, the sub-pages placed back on the free lists > > lose the PageReported flag. This means they will be unnecessarily > > re-reported to the hypervisor in the next reporting cycle, wasting > > work. > > > > Is this issue generated by the changes in the overall patch set, or an > issue present regardless of the proposed zeroing avoidance feature? > > If the former, then maybe just submit as a standalone patch, seems like > a useful improvement regardless. The former but then the only issue is more reporting, and I couldn't find a benchmark that would quantify the performance difference. So the value of pushing a fix by itself is pretty low. > If fundamentally tied to the zeroing-avoidance feature, then nudging > this to the front or end of the series (depending on conflicts) would > help focus the review of the core new feature. > > ~Gregory I can nudge it forward sure. -- MST