From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 9E2E52C0212 for ; Wed, 19 Feb 2014 11:41:06 +1100 (EST) Received: from /spool/local by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 18 Feb 2014 17:41:03 -0700 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp02.boulder.ibm.com (Postfix) with ESMTP id B869A3E4003E for ; Tue, 18 Feb 2014 17:41:01 -0700 (MST) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by b03cxnp08025.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s1J0f1Q5786722 for ; Wed, 19 Feb 2014 01:41:01 +0100 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s1J0f1Rj000880 for ; Tue, 18 Feb 2014 17:41:01 -0700 Date: Tue, 18 Feb 2014 16:40:54 -0800 From: Nishanth Aravamudan To: Michal Hocko Subject: Re: ppc: RECLAIM_DISTANCE 10? Message-ID: <20140219004053.GA27108@linux.vnet.ibm.com> References: <20140218090658.GA28130@dhcp22.suse.cz> <20140218233404.GB10844@linux.vnet.ibm.com> <20140218235800.GC10844@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20140218235800.GC10844@linux.vnet.ibm.com> Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Anton Blanchard , LKML List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 18.02.2014 [15:58:00 -0800], Nishanth Aravamudan wrote: > On 18.02.2014 [15:34:05 -0800], Nishanth Aravamudan wrote: > > Hi Michal, > > > > On 18.02.2014 [10:06:58 +0100], Michal Hocko wrote: > > > Hi, > > > I have just noticed that ppc has RECLAIM_DISTANCE reduced to 10 set by > > > 56608209d34b (powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to > > > enable zone reclaim). The commit message suggests that the zone reclaim > > > is desirable for all NUMA configurations. > > > > > > History has shown that the zone reclaim is more often harmful than > > > helpful and leads to performance problems. The default RECLAIM_DISTANCE > > > for generic case has been increased from 20 to 30 around 3.0 > > > (32e45ff43eaf mm: increase RECLAIM_DISTANCE to 30). > > > > Interesting. > > > > > I strongly suspect that the patch is incorrect and it should be > > > reverted. Before I will send a revert I would like to understand what > > > led to the patch in the first place. I do not see why would PPC use only > > > LOCAL_DISTANCE and REMOTE_DISTANCE distances and in fact machines I have > > > seen use different values. > > > > > > Anton, could you comment please? > > > > I'll let Anton comment here, but in looking into this issue in working > > on CONFIG_HAVE_MEMORYLESS_NODE support, I realized that any LPAR with > > memoryless nodes will set zone_reclaim_mode to 1. I think we want to > > ignore memoryless nodes when we set up the reclaim mode like the > > following? I'll send it as a proper patch if you agree? > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 5de4337..4f6ff6f 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1853,8 +1853,9 @@ static void __paginginit init_zone_allows_reclaim(int nid) > > { > > int i; > > > > - for_each_online_node(i) > > - if (node_distance(nid, i) <= RECLAIM_DISTANCE) > > + for_each_online_node(i) { > > + if (node_distance(nid, i) <= RECLAIM_DISTANCE || > > + local_memory_node(nid) != nid) > > node_set(i, NODE_DATA(nid)->reclaim_nodes); > > else > > zone_reclaim_mode = 1; > > > > Note, this won't actually do anything if CONFIG_HAVE_MEMORYLESS_NODES is > > not set, but if it is, I think semantically it will indicate that > > memoryless nodes *have* to reclaim remotely. > > > > And actually the above won't work, because the callpath is > > > > start_kernel -> setup_arch -> paging_init [-> free_area_init_nodes -> > > free_area_init_node -> init_zone_allows_reclaim] which is called before > > build_all_zonelists. This is a similar ordering problem as I'm having > > with the MEMORYLESS_NODE support, will work on it. > > How about the following? > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5de4337..1a0eced 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1854,7 +1854,8 @@ static void __paginginit init_zone_allows_reclaim(int nid) > int i; > > for_each_online_node(i) > - if (node_distance(nid, i) <= RECLAIM_DISTANCE) > + if (node_distance(nid, i) <= RECLAIM_DISTANCE || > + !NODE_DATA(nid)->node_present_pages) err s/nid/i/ above. -Nish