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X-CSE-ConnectionGUID: KxoMV4qYRceVP9PZn+aJIA== X-CSE-MsgGUID: qG+PivujRHONXEmbgYhY/w== X-IronPort-AV: E=McAfee;i="6700,10204,11129"; a="21912595" X-IronPort-AV: E=Sophos;i="6.09,199,1716274800"; d="scan'208";a="21912595" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2024 23:44:29 -0700 X-CSE-ConnectionGUID: FWvK/SEfSMSGuSzsStRCBA== X-CSE-MsgGUID: sbJhTeT7Q7mFhu4vUOXqSg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.09,199,1716274800"; d="scan'208";a="48218799" Received: from unknown (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2024 23:44:28 -0700 From: "Huang, Ying" To: Yafang Shao Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, linux-mm@kvack.org, Matthew Wilcox , David Rientjes Subject: Re: [PATCH 3/3] mm/page_alloc: Introduce a new sysctl knob vm.pcp_batch_scale_max In-Reply-To: (Yafang Shao's message of "Thu, 11 Jul 2024 10:21:34 +0800") References: <20240707094956.94654-1-laoar.shao@gmail.com> <20240707094956.94654-4-laoar.shao@gmail.com> <878qyaarm6.fsf@yhuang6-desk2.ccr.corp.intel.com> Date: Thu, 11 Jul 2024 14:42:36 +0800 Message-ID: <87o774a0pv.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: xhdsbpjijkiquoknee3x18ynckoeesbc X-Rspam-User: X-Rspamd-Queue-Id: 85B162001B X-Rspamd-Server: rspam02 X-HE-Tag: 1720680270-157352 X-HE-Meta: U2FsdGVkX1/gUO0Ef4gWzaDVcRyax4TcVi3ApKoTSvmyfVnXb9jUtHItQNrWl1SBoUAKhM17Aeh6BIWD8Q0luu800YWpVD+CfqSO7XlVWO14zd8vpK0SDWmca8Fohe9b7BeGuJYrl6rY44xZ/wz+0CxHmgZ+J0xAONRdfRdBT1P9TRRoY/zx5N0S0ET7rnxbnRdmUxRuwGJUNmSU82O1mi67z9+fpBMOvGy5NWG+ImKF2dIBX37WvOFzM9HUtAtabJxAboa9OFQcmDYF0Y0axmt1ewJeoaHmPNegCYYlZ7I+wz4KtWf58VLIJaEzcsuu8h/KFgKmYw/0qLU2iOg25NAAmp2nDFZJg4mtoMhwHUEbBpvLEfCE5jodV1HZqYVyuUFTQTZmizDg//Pqg1trsZ6x2VDr1Uh55lBmuju6AfuJUQfWldjXkxMLyQmmSVtg6xsGE/dt7lWrr1nHQUwc0O8dKId73idTtUlkx3225STw2gJiTS3RJt9EnUWdGUdLDS+SD0G68DySnwop3V6fmkP3lUElss8n35tpltT7wt8053i80uAp7JROXQsjzqztMP53Z8bX0niAnl2agw6pfLJXhsLkQA9kyWHUxcBJ8lrhBMx2z0N/mEpDrOLmuYILAyp2B7Tg9uRG8One1yb5iUNZWw02HrmW+9rOA12u23XIsqxeC4W9RA0/tiF+N0Bk/uKB5RUNcnCPWyp+8J/Pu+kubOY58hbk+KLat9G4FzeUVi9CqxbcJdpYG2KxmN+7LRRBzWml5e+vL+zh78sFVy3QZZiQwV1yKTN7OGpE1lALw86Rp+8Xf+qo0i8yf5j+xrnshUKWrGBBucnqyb5ydO7hnLwy5m7CJGck0Op9OnRcTfXIkJ2B8VQx36htUcrURjdlLOQO8WQF/1Ma66mXopP1kbOFcEq0AoBCYVr6sRnQ07syswFvYvRCejvCLJCwCHi7rkTLU0MixbaOqK9 6vb+FGYi i+5+sJOvCQnekZBM0HEJAmQZdOC71vousa67xqmLM66a+88WsTwxi7wV7PfPnrsrE3Ls3YxEFcI3VWr4nKIZDAKPbfvhSpA5b1XovCaPXyXxQu/sDKq1DqzPsy3gYGEafnhWNWrxfKygDCCqtfxfXz19p60l7kGcK0U6ZXJJ+0OrHe5iPnbIbEJ8K8lVDZbe0tBIVFn5T3NJYVmdIHGjK9htdXHv0ukKXla3fU9pwcLi8zPHAohrzKDqwCakS/7QorMuxrhG37OamIBu0f0gj738SBXheJw3VWS0jUKRBq4VegponNzIs5YWdUg== 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: Yafang Shao writes: > On Wed, Jul 10, 2024 at 10:51=E2=80=AFAM Huang, Ying wrote: >> >> Yafang Shao writes: >> >> > The configuration parameter PCP_BATCH_SCALE_MAX poses challenges for >> > quickly experimenting with specific workloads in a production environm= ent, >> > particularly when monitoring latency spikes caused by contention on the >> > zone->lock. To address this, a new sysctl parameter vm.pcp_batch_scale= _max >> > is introduced as a more practical alternative. >> >> In general, I'm neutral to the change. I can understand that kernel >> configuration isn't as flexible as sysctl knob. But, sysctl knob is ABI >> too. >> >> > To ultimately mitigate the zone->lock contention issue, several sugges= tions >> > have been proposed. One approach involves dividing large zones into mu= lti >> > smaller zones, as suggested by Matthew[0], while another entails split= ting >> > the zone->lock using a mechanism similar to memory arenas and shifting= away >> > from relying solely on zone_id to identify the range of free lists a >> > particular page belongs to[1]. However, implementing these solutions is >> > likely to necessitate a more extended development effort. >> >> Per my understanding, the change will hurt instead of improve zone->lock >> contention. Instead, it will reduce page allocation/freeing latency. > > I'm quite perplexed by your recent comment. You introduced a > configuration that has proven to be difficult to use, and you have > been resistant to suggestions for modifying it to a more user-friendly > and practical tuning approach. May I inquire about the rationale > behind introducing this configuration in the beginning? Sorry, I don't understand your words. Do you need me to explain what is "neutral"? -- Best Regards, Huang, Ying