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Message-ID: <6d40d60e-dde4-7d70-c7a8-1a444c70c3ff@intel.com> Date: Thu, 11 Apr 2019 09:06:00 -0700 From: Dave Hansen <dave.hansen@...el.com> To: Yang Shi <yang.shi@...ux.alibaba.com>, mhocko@...e.com, mgorman@...hsingularity.net, riel@...riel.com, hannes@...xchg.org, akpm@...ux-foundation.org, keith.busch@...el.com, dan.j.williams@...el.com, fengguang.wu@...el.com, fan.du@...el.com, ying.huang@...el.com, ziy@...dia.com Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [v2 PATCH 7/9] mm: vmscan: check if the demote target node is contended or not On 4/10/19 8:56 PM, Yang Shi wrote: > When demoting to PMEM node, the target node may have memory pressure, > then the memory pressure may cause migrate_pages() fail. > > If the failure is caused by memory pressure (i.e. returning -ENOMEM), > tag the node with PGDAT_CONTENDED. The tag would be cleared once the > target node is balanced again. > > Check if the target node is PGDAT_CONTENDED or not, if it is just skip > demotion. This seems like an actively bad idea to me. Why do we need an *active* note to say the node is contended? Why isn't just getting a failure back from migrate_pages() enough? Have you observed this in practice?
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