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X-IronPort-AV: E=McAfee;i="6600,9927,10946"; a="4570328" X-IronPort-AV: E=Sophos;i="6.04,340,1695711600"; d="scan'208";a="4570328" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jan 2024 23:10:09 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10946"; a="1028315259" X-IronPort-AV: E=Sophos;i="6.04,340,1695711600"; d="scan'208";a="1028315259" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jan 2024 23:10:03 -0800 From: "Huang, Ying" To: Gregory Price Cc: Gregory Price , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Srinivasulu Thanneeru Subject: Re: [PATCH v5 02/11] mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving In-Reply-To: (Gregory Price's message of "Fri, 5 Jan 2024 02:25:28 -0500") References: <20231223181101.1954-3-gregory.price@memverge.com> <8734vof3kq.fsf@yhuang6-desk2.ccr.corp.intel.com> <878r58dt31.fsf@yhuang6-desk2.ccr.corp.intel.com> <87mstnc6jz.fsf@yhuang6-desk2.ccr.corp.intel.com> <875y09d5d8.fsf@yhuang6-desk2.ccr.corp.intel.com> <87cyugb7cz.fsf@yhuang6-desk2.ccr.corp.intel.com> Date: Mon, 08 Jan 2024 15:08:05 +0800 Message-ID: <87mstg9uay.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Stat-Signature: bwfwq9u96xku3u3mznhuqh6nqa6wnqjb X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C13E8180010 X-HE-Tag: 1704697811-240150 X-HE-Meta: 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 OaqEbofO PceTUFkT58Ep4iYnnhkKh4wvfqEhlgqI5D7A461g48S/iVBC3lt7e3Js8D0KlTe6Ua/lWoa7S8Fa2iT99dZqX6p8F9YryO3Jj+yEcdWjgcnMhKiE34w7FIZr8AWlw6Ec8R5Y2bFTzbsL3mFoa2auLAcuG4jpZ7Hs8HwmuWVFnTg7XRWoPGr59vIP0DH1hdkTCuSJMjMdrcF6OroxydVFDGCUSYKnCJjSMVOzIJikoWcsZvgwKb6hIrcY5UBe2nB3gQSWW0WUsaFDjbP2em494j8XWLvlSqgHRtFG70u8z+HWfu2h4WEgNSzwcT2VkHeixjkCOOr6x2GbomOg= 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: Gregory Price writes: > On Fri, Jan 05, 2024 at 02:51:40PM +0800, Huang, Ying wrote: >> > >> > So we're talking ~1MB for 1024 threads with mempolicies to avoid error >> > conditions mid-page-allocation and to reduce the cost associated with >> > applying weighted interleave. >> >> Think about this again. Why do we need weights array on stack? I think >> this is used to keep weights consistent. If so, we don't need weights >> array on stack. Just use RCU to access global weights array. >> > > From the bulk allocation code: > > __alloc_pages_bulk(gfp, node, NULL, node_pages, NULL, page_array); > > This function can block. You cannot block during an RCU read context. Yes. You are right. For __alloc_pages_bulk(), it should be OK to allocate the weights array. For weighted_interleave_nid(), we can use RCU to avoid memory allocation in relative fast code path. BTW, we can use nr_node_ids instead of MAX_NUMNODES if applicable. -- Best Regards, Huang, Ying