From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C388BC433EF for ; Mon, 6 Jun 2022 07:43:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231222AbiFFHn1 (ORCPT ); Mon, 6 Jun 2022 03:43:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43720 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231194AbiFFHnX (ORCPT ); Mon, 6 Jun 2022 03:43:23 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAC014477E for ; Mon, 6 Jun 2022 00:43:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1654501401; x=1686037401; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=Nih0XtibWMqFGEJeN6Inq6uUDsRlovvem8SyO9Pcv+k=; b=WoBLdqeAm2Q60FiFsVc9aAmXLMd5WI7NnzoePWuqtC3WvrSKo8BPoNVq TSEdpiZeaou8XmvMe4dHX8D5wMsAhoNNvWhxrI1/qXmgm2B/CUk1NtcTl hWEuoOIcnP578z5GbZS93yhajvQA6qWLPGZDyplDgTstsCkTs6UqWu2jg UhVe+blJybBmO3/nm/GwBrWoixGAeu1QRiqJ4EeepiXvN7NH0w5XuOaVF shUY1p8wfyvS+XqW8xD41zz4DZlTiCdOHJHwFu445FUp1yLNLT55wuk28 4Fsc/hz7c5N7sckKWHkiBZpTR6NMoG0zvJIIbM0XXAaLRHWfeEJ+9MSHb A==; X-IronPort-AV: E=McAfee;i="6400,9594,10369"; a="264463293" X-IronPort-AV: E=Sophos;i="5.91,280,1647327600"; d="scan'208";a="264463293" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jun 2022 00:43:11 -0700 X-IronPort-AV: E=Sophos;i="5.91,280,1647327600"; d="scan'208";a="583496939" Received: from xingguom-mobl.ccr.corp.intel.com ([10.254.213.116]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jun 2022 00:43:03 -0700 Message-ID: Subject: Re: [RFC PATCH v4 7/7] mm/demotion: Demote pages according to allocation fallback order From: Ying Huang To: "Aneesh Kumar K.V" , linux-mm@kvack.org, akpm@linux-foundation.org Cc: Greg Thelen , Yang Shi , Davidlohr Bueso , Tim C Chen , Brice Goglin , Michal Hocko , Linux Kernel Mailing List , Hesham Almatary , Dave Hansen , Jonathan Cameron , Alistair Popple , Dan Williams , Feng Tang , Jagdish Gediya , Baolin Wang , David Rientjes Date: Mon, 06 Jun 2022 15:42:58 +0800 In-Reply-To: <87leua8g7s.fsf@linux.ibm.com> References: <20220527122528.129445-1-aneesh.kumar@linux.ibm.com> <20220527122528.129445-8-aneesh.kumar@linux.ibm.com> <046c373a-f30b-091d-47a1-e28bfb7e9394@linux.ibm.com> <9f6e60cc8be3cbde4871458c612c5c31d2a9e056.camel@intel.com> <65919df6b3302741780ff6fa69e497af06a9825e.camel@intel.com> <87leua8g7s.fsf@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.3-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2022-06-06 at 11:51 +0530, Aneesh Kumar K.V wrote: > Ying Huang writes: > > ..... > > > > > > > > > > > > https://lore.kernel.org/lkml/69f2d063a15f8c4afb4688af7b7890f32af55391.camel@intel.com/ > > > > > > > > > > > > That is, something like below, > > > > > > > > > > > > static struct page *alloc_demote_page(struct page *page, unsigned long node) > > > > > > { > > > > > > struct page *page; > > > > > > nodemask_t allowed_mask; > > > > > > struct migration_target_control mtc = { > > > > > > /* > > > > > > * Allocate from 'node', or fail quickly and quietly. > > > > > > * When this happens, 'page' will likely just be discarded > > > > > > * instead of migrated. > > > > > > */ > > > > > > .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | > > > > > > __GFP_THISNODE | __GFP_NOWARN | > > > > > > __GFP_NOMEMALLOC | GFP_NOWAIT, > > > > > > .nid = node > > > > > > }; > > > > > > > > > > > > page = alloc_migration_target(page, (unsigned long)&mtc); > > > > > > if (page) > > > > > > return page; > > > > > > > > > > > > mtc.gfp_mask &= ~__GFP_THISNODE; > > > > > > mtc.nmask = &allowed_mask; > > > > > > > > > > > > return alloc_migration_target(page, (unsigned long)&mtc); > > > > > > } > > > > > > > > > > I skipped doing this in v5 because I was not sure this is really what we > > > > > want. > > > > > > > > I think so. And this is the original behavior. We should keep the > > > > original behavior as much as possible, then make changes if necessary. > > > > > > > > > > That is the reason I split the new page allocation as a separate patch. > > > Previous discussion on this topic didn't conclude on whether we really > > > need to do the above or not > > > https://lore.kernel.org/lkml/CAAPL-u9endrWf_aOnPENDPdvT-2-YhCAeJ7ONGckGnXErTLOfQ@mail.gmail.com/ > > > > Please check the later email in the thread you referenced. Both Wei and > > me agree that the use case needs to be supported. We just didn't reach > > concensus about how to implement it. If you think Wei's solution is > > better (referenced as below), you can try to do that too. Although I > > think my proposed implementation is much simpler. > > How about the below details > > diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h > index 79bd8d26feb2..cd6e71f702ad 100644 > --- a/include/linux/memory-tiers.h > +++ b/include/linux/memory-tiers.h > @@ -21,6 +21,7 @@ void node_remove_from_memory_tier(int node); >  int node_get_memory_tier_id(int node); >  int node_set_memory_tier(int node, int tier); >  int node_reset_memory_tier(int node, int tier); > +void node_get_allowed_targets(int node, nodemask_t *targets); >  #else >  #define numa_demotion_enabled false >  static inline int next_demotion_node(int node) > @@ -28,6 +29,10 @@ static inline int next_demotion_node(int node) >   return NUMA_NO_NODE; >  } >   > > > > +static inline void node_get_allowed_targets(int node, nodemask_t *targets) > +{ > + *targets = NODE_MASK_NONE; > +} >  #endif /* CONFIG_TIERED_MEMORY */ >   > > > >  #endif > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c > index b4e72b672d4d..592d939ec28d 100644 > --- a/mm/memory-tiers.c > +++ b/mm/memory-tiers.c > @@ -18,6 +18,7 @@ struct memory_tier { >   > > > >  struct demotion_nodes { >   nodemask_t preferred; > + nodemask_t allowed; >  }; >   > > > >  #define to_memory_tier(device) container_of(device, struct memory_tier, dev) > @@ -378,6 +379,25 @@ int node_set_memory_tier(int node, int tier) >  } >  EXPORT_SYMBOL_GPL(node_set_memory_tier); >   > > > > +void node_get_allowed_targets(int node, nodemask_t *targets) > +{ > + /* > + * node_demotion[] is updated without excluding this > + * function from running. > + * > + * If any node is moving to lower tiers then modifications > + * in node_demotion[] are still valid for this node, if any > + * node is moving to higher tier then moving node may be > + * used once for demotion which should be ok so rcu should > + * be enough here. > + */ > + rcu_read_lock(); > + > + *targets = node_demotion[node].allowed; > + > + rcu_read_unlock(); > +} > + >  /** >   * next_demotion_node() - Get the next node in the demotion path >   * @node: The starting node to lookup the next node > @@ -437,8 +457,10 @@ static void __disable_all_migrate_targets(void) >  { >   int node; >   > > > > - for_each_node_mask(node, node_states[N_MEMORY]) > + for_each_node_mask(node, node_states[N_MEMORY]) { >   node_demotion[node].preferred = NODE_MASK_NONE; > + node_demotion[node].allowed = NODE_MASK_NONE; > + } >  } >   > > > >  static void disable_all_migrate_targets(void) > @@ -465,7 +487,7 @@ static void establish_migration_targets(void) >   struct demotion_nodes *nd; >   int target = NUMA_NO_NODE, node; >   int distance, best_distance; > - nodemask_t used; > + nodemask_t used, allowed = NODE_MASK_NONE; >   > > > >   if (!node_demotion) >   return; > @@ -511,6 +533,29 @@ static void establish_migration_targets(void) >   } >   } while (1); >   } > + /* > + * Now build the allowed mask for each node collecting node mask from > + * all memory tier below it. This allows us to fallback demotion page > + * allocation to a set of nodes that is closer the above selected > + * perferred node. > + */ > + list_for_each_entry(memtier, &memory_tiers, list) > + nodes_or(allowed, allowed, memtier->nodelist); > + /* > + * Removes nodes not yet in N_MEMORY. > + */ > + nodes_and(allowed, node_states[N_MEMORY], allowed); > + > + list_for_each_entry(memtier, &memory_tiers, list) { > + /* > + * Keep removing current tier from allowed nodes, > + * This will remove all nodes in current and above > + * memory tier from the allowed mask. > + */ > + nodes_andnot(allowed, allowed, memtier->nodelist); > + for_each_node_mask(node, memtier->nodelist) > + node_demotion[node].allowed = allowed; > + } >  } >   > > > >  /* > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 3a8f78277f99..b0792d838efb 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1460,19 +1460,32 @@ static void folio_check_dirty_writeback(struct folio *folio, >   mapping->a_ops->is_dirty_writeback(folio, dirty, writeback); >  } >   > > > > -static struct page *alloc_demote_page(struct page *page, unsigned long node) > +static struct page *alloc_demote_page(struct page *page, unsigned long private) >  { > - struct migration_target_control mtc = { > - /* > - * Allocate from 'node', or fail quickly and quietly. > - * When this happens, 'page' will likely just be discarded > - * instead of migrated. > - */ > - .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | > - __GFP_THISNODE | __GFP_NOWARN | > - __GFP_NOMEMALLOC | GFP_NOWAIT, > - .nid = node > - }; > + struct page *target_page; > + nodemask_t *allowed_mask; > + struct migration_target_control *mtc; > + > + mtc = (struct migration_target_control *)private; > + > + allowed_mask = mtc->nmask; > + /* > + * make sure we allocate from the target node first also trying to > + * reclaim pages from the target node via kswapd if we are low on > + * free memory on target node. If we don't do this and if we have low > + * free memory on the target memtier, we would start allocating pages > + * from higher memory tiers without even forcing a demotion of cold > + * pages from the target memtier. This can result in the kernel placing > + * hotpages in higher memory tiers. > + */ > + mtc->nmask = NULL; > + mtc->gfp_mask |= __GFP_THISNODE; > + target_page = alloc_migration_target(page, (unsigned long)&mtc); > + if (target_page) > + return target_page; > + > + mtc->gfp_mask &= ~__GFP_THISNODE; > + mtc->nmask = allowed_mask; >   > > > >   return alloc_migration_target(page, (unsigned long)&mtc); >  } > @@ -1487,6 +1500,19 @@ static unsigned int demote_page_list(struct list_head *demote_pages, >  { >   int target_nid = next_demotion_node(pgdat->node_id); >   unsigned int nr_succeeded; > + nodemask_t allowed_mask; > + > + struct migration_target_control mtc = { > + /* > + * Allocate from 'node', or fail quickly and quietly. > + * When this happens, 'page' will likely just be discarded > + * instead of migrated. > + */ > + .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN | > + __GFP_NOMEMALLOC | GFP_NOWAIT, > + .nid = target_nid, > + .nmask = &allowed_mask > + }; >   > > > >   if (list_empty(demote_pages)) >   return 0; > @@ -1494,10 +1520,12 @@ static unsigned int demote_page_list(struct list_head *demote_pages, >   if (target_nid == NUMA_NO_NODE) >   return 0; >   > > > > + node_get_allowed_targets(pgdat->node_id, &allowed_mask); > + >   /* Demotion ignores all cpuset and mempolicy settings */ >   migrate_pages(demote_pages, alloc_demote_page, NULL, > - target_nid, MIGRATE_ASYNC, MR_DEMOTION, > - &nr_succeeded); > + (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION, > + &nr_succeeded); Firstly, it addressed my requirement, Thanks! And, I'd prefer to put mtc definition in alloc_demote_page(). Because that makes all page allocation logic in one function. Thus the readability of code is better. Best Regards, Huang, Ying >   if (current_is_kswapd()) >   __count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);