From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4E8485BAC7 for ; Tue, 20 Feb 2024 08:00:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708416011; cv=none; b=UcQAt6DaP0mhCNFTH4Zy4CZBpwLc2FGbm2bHD8MiTGeIAmWy6+eBpiuRMuUZMXeCaDJO0YSySTQYZW3xyjSwWvNDB7ICJvfZ9y15gO4ZubP6F3Z1K66+JnDV2GZSID8RxB8Z08JK0l+/QI7pZeSwAmN0fHZQF+r6jWWkrWoQIKI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708416011; c=relaxed/simple; bh=eZv6WUm7V6V+iGmNDQJxOZcEkeJtxjVLwn7qbkKSKT4=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=WXAn61h2HNxb+CaMj/ceJpiKDFq0H4UBUiws3lRtnKFFDD2VjNA3sCkw88bioWGUJGyyvD6OvJhXWAUDon/7OLM+wp2rrEnaZsFN3NTnL8CPhfqTtxGDsfIaX4ls+l/WjzFJz6uyfCfQma3x+twHywRZYksSZXENwFi8hdGm2P8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=jkiIiBt9; arc=none smtp.client-ip=198.175.65.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="jkiIiBt9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1708416010; x=1739952010; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=eZv6WUm7V6V+iGmNDQJxOZcEkeJtxjVLwn7qbkKSKT4=; b=jkiIiBt9+HVpYDvpw/JGnOzvuAj5QUwgE5DjmcceP6kPEjmp1qt7NXTh eWcaKGPZWlU4aIibdegsWOmk9CzUWMhYDAHvXMPZ9k2AhVC5k3EZbJIOr mRTd1GF/ti8NjMeAMpi/ISU5UJbox1glQkgfTY5e5rNKq33QmgRmUPmX/ SLA1bEUQ4C5Ng4UaAQ4r9z0pxIytJeKjsNcdE7cUUIO0dO9WD3xjBA24W m5m/180P/Ly0lPrEf9ZFzqrH6UzkCi8WhnADTKCW04ddaf7/2+JqS6igX OeC7B1PtNFPespRCIRRk70A+NO9djkdBADAnzqOlfabqYWZgEbtL5ZPxY Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10989"; a="19942755" X-IronPort-AV: E=Sophos;i="6.06,172,1705392000"; d="scan'208";a="19942755" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Feb 2024 00:00:09 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.06,172,1705392000"; d="scan'208";a="5064774" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Feb 2024 00:00:03 -0800 From: "Huang, Ying" To: Aneesh Kumar K.V Cc: Donet Tom , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen , Mel Gorman , Ben Widawsky , Feng Tang , Michal Hocko , Andrea Arcangeli , Peter Zijlstra , Ingo Molnar , Rik van Riel , Johannes Weiner , Matthew Wilcox , Mike Kravetz , Vlastimil Babka , Dan Williams , Hugh Dickins , Kefeng Wang , Suren Baghdasaryan Subject: Re: [PATCH 3/3] mm/numa_balancing:Allow migrate on protnone reference with MPOL_PREFERRED_MANY policy In-Reply-To: <87sf1nzi3s.fsf@kernel.org> (Aneesh Kumar K. V.'s message of "Tue, 20 Feb 2024 13:23:59 +0530") References: <9c3f7b743477560d1c5b12b8c111a584a2cc92ee.1708097962.git.donettom@linux.ibm.com> <8d7737208bd24e754dc7a538a3f7f02de84f1f72.1708097962.git.donettom@linux.ibm.com> <877cizppsa.fsf@yhuang6-desk2.ccr.corp.intel.com> <87sf1nzi3s.fsf@kernel.org> Date: Tue, 20 Feb 2024 15:58:08 +0800 Message-ID: <87ttm3o9db.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) 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=ascii Aneesh Kumar K.V writes: > "Huang, Ying" writes: > >> Donet Tom writes: >> >>> commit bda420b98505 ("numa balancing: migrate on fault among multiple bound >>> nodes") added support for migrate on protnone reference with MPOL_BIND >>> memory policy. This allowed numa fault migration when the executing node >>> is part of the policy mask for MPOL_BIND. This patch extends migration >>> support to MPOL_PREFERRED_MANY policy. >>> >>> Currently, we cannot specify MPOL_PREFERRED_MANY with the mempolicy flag >>> MPOL_F_NUMA_BALANCING. This causes issues when we want to use >>> NUMA_BALANCING_MEMORY_TIERING. To effectively use the slow memory tier, >>> the kernel should not allocate pages from the slower memory tier via >>> allocation control zonelist fallback. Instead, we should move cold pages >>> from the faster memory node via memory demotion. For a page allocation, >>> kswapd is only woken up after we try to allocate pages from all nodes in >>> the allocation zone list. This implies that, without using memory >>> policies, we will end up allocating hot pages in the slower memory tier. >>> >>> MPOL_PREFERRED_MANY was added by commit b27abaccf8e8 ("mm/mempolicy: add >>> MPOL_PREFERRED_MANY for multiple preferred nodes") to allow better >>> allocation control when we have memory tiers in the system. With >>> MPOL_PREFERRED_MANY, the user can use a policy node mask consisting only >>> of faster memory nodes. When we fail to allocate pages from the faster >>> memory node, kswapd would be woken up, allowing demotion of cold pages >>> to slower memory nodes. >>> >>> With the current kernel, such usage of memory policies implies we can't >>> do page promotion from a slower memory tier to a faster memory tier >>> using numa fault. This patch fixes this issue. >>> >>> For MPOL_PREFERRED_MANY, if the executing node is in the policy node >>> mask, we allow numa migration to the executing nodes. If the executing >>> node is not in the policy node mask but the folio is already allocated >>> based on policy preference (the folio node is in the policy node mask), >>> we don't allow numa migration. If both the executing node and folio node >>> are outside the policy node mask, we allow numa migration to the >>> executing nodes. >>> >>> Signed-off-by: Aneesh Kumar K.V (IBM) >>> Signed-off-by: Donet Tom >>> --- >>> mm/mempolicy.c | 28 ++++++++++++++++++++++++++-- >>> 1 file changed, 26 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c >>> index 73d698e21dae..8c4c92b10371 100644 >>> --- a/mm/mempolicy.c >>> +++ b/mm/mempolicy.c >>> @@ -1458,9 +1458,10 @@ static inline int sanitize_mpol_flags(int *mode, unsigned short *flags) >>> if ((*flags & MPOL_F_STATIC_NODES) && (*flags & MPOL_F_RELATIVE_NODES)) >>> return -EINVAL; >>> if (*flags & MPOL_F_NUMA_BALANCING) { >>> - if (*mode != MPOL_BIND) >>> + if (*mode == MPOL_BIND || *mode == MPOL_PREFERRED_MANY) >>> + *flags |= (MPOL_F_MOF | MPOL_F_MORON); >>> + else >>> return -EINVAL; >>> - *flags |= (MPOL_F_MOF | MPOL_F_MORON); >>> } >>> return 0; >>> } >>> @@ -2463,6 +2464,23 @@ static void sp_free(struct sp_node *n) >>> kmem_cache_free(sn_cache, n); >>> } >>> >>> +static inline bool mpol_preferred_should_numa_migrate(int exec_node, int folio_node, >>> + struct mempolicy *pol) >>> +{ >>> + /* if the executing node is in the policy node mask, migrate */ >>> + if (node_isset(exec_node, pol->nodes)) >>> + return true; >>> + >>> + /* If the folio node is in policy node mask, don't migrate */ >>> + if (node_isset(folio_node, pol->nodes)) >>> + return false; >>> + /* >>> + * both the folio node and executing node are outside the policy nodemask, >>> + * migrate as normal numa fault migration. >>> + */ >>> + return true; >> >> Why? This may cause some unexpected result. For example, pages may be >> distributed among multiple sockets unexpectedly. So, I prefer the more >> conservative policy, that is, only migrate if this node is in >> pol->nodes. >> > > This will only have an impact if the user specifies > MPOL_F_NUMA_BALANCING. This means that the user is explicitly requesting > for frequently accessed memory pages to be migrated. Memory policy > MPOL_PREFERRED_MANY is able to allocate pages from nodes outside of > policy->nodes. For the specific use case that I am interested in, it > should be okay to restrict it to policy->nodes. However, I am wondering > if this is too restrictive given the definition of MPOL_PREFERRED_MANY. IMHO, we can start with some consecutive way and expand it if it's proved necessary. -- Best Regards, Huang, Ying