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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kas@kernel.org, shakeel.butt@linux.dev, usama.arif@linux.dev, kernel-team@meta.com Subject: Re: [PATCH] mm/vmstat: spread vmstat_update requeue across the stat interval Message-ID: References: <20260401-vmstat-v1-1-b68ce4a35055@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260401-vmstat-v1-1-b68ce4a35055@debian.org> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E693B40005 X-Stat-Signature: 6fwwiijqt8ff5d384a5ao16kkx619faw X-HE-Tag: 1775134182-477186 X-HE-Meta: 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 sMaSibxQ 0dRGo6Jy+8RLOEYcF8n+QxNCrRr7raHZtfzJTD3VwXeT1oXYaGWpCkfKMuXaVXUFNoa7hzkidCUMHct5eVLbIDDxnuWBTwgSTpIrrGcsv/02C+OJNjvO1WvHwTuzYNrsYw3lZz/Op4a5iRSYhMrF8LXVF7fzBDjLEVKQ4TrSavyYCyAgevVy2QOftISrxQNIAw59puM+eXfJ48rFBHWb7EuXLpDeZNnVhsKZv+adU+4NPmnVWX5L37F+psDUUjOs6Hk2AvHS6cGHto1bni0M5JeIp67rE4dEpppIIIIDZLVpU2Z0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 01, 2026 at 06:57:50AM -0700, Breno Leitao wrote: > vmstat_update uses round_jiffies_relative() when re-queuing itself, > which aligns all CPUs' timers to the same second boundary. When many > CPUs have pending PCP pages to drain, they all call decay_pcp_high() -> > free_pcppages_bulk() simultaneously, serializing on zone->lock and > hitting contention. > > Introduce vmstat_spread_delay() which distributes each CPU's > vmstat_update evenly across the stat interval instead of aligning them. But, uh, round_jiffies_relative() is _supposed_ to do that! Look at both the documentation and implementation. Why isn't it working?