From: Shakeel Butt <firstname.lastname@example.org> To: Dave Hansen <email@example.com> Cc: LKML <firstname.lastname@example.org>, Linux MM <email@example.com>, Yang Shi <firstname.lastname@example.org>, David Rientjes <email@example.com>, Huang Ying <firstname.lastname@example.org>, Dan Williams <email@example.com> Subject: Re: [RFC][PATCH 0/8] Migrate Pages in lieu of discard Date: Tue, 30 Jun 2020 11:36:43 -0700 Message-ID: <CALvZod55OFzOozsDbyTkUh1uZEobo4CZ=+8JgrJJHw8QuWh0hw@mail.gmail.com> (raw) In-Reply-To: <20200629234503.749E5340@viggo.jf.intel.com> On Mon, Jun 29, 2020 at 4:48 PM Dave Hansen <firstname.lastname@example.org> wrote: > > I've been sitting on these for too long. Tha main purpose of this > post is to have a public discussion with the other folks who are > interested in this functionalty and converge on a single > implementation. > > This set directly incorporates a statictics patch from Yang Shi and > also includes one to ensure good behavior with cgroup reclaim which > was very closely derived from this series: > > https://email@example.com/ > > Since the last post, the major changes are: > - Added patch to skip migration when doing cgroup reclaim > - Added stats patch from Yang Shi > > The full series is also available here: > > https://github.com/hansendc/linux/tree/automigrate-20200629 > > -- > > We're starting to see systems with more and more kinds of memory such > as Intel's implementation of persistent memory. > > Let's say you have a system with some DRAM and some persistent memory. > Today, once DRAM fills up, reclaim will start and some of the DRAM > contents will be thrown out. Allocations will, at some point, start > falling over to the slower persistent memory. > > That has two nasty properties. First, the newer allocations can end > up in the slower persistent memory. Second, reclaimed data in DRAM > are just discarded even if there are gobs of space in persistent > memory that could be used. > > This set implements a solution to these problems. At the end of the > reclaim process in shrink_page_list() just before the last page > refcount is dropped, the page is migrated to persistent memory instead > of being dropped. > > While I've talked about a DRAM/PMEM pairing, this approach would > function in any environment where memory tiers exist. > > This is not perfect. It "strands" pages in slower memory and never > brings them back to fast DRAM. Other things need to be built to > promote hot pages back to DRAM. > > This is part of a larger patch set. If you want to apply these or > play with them, I'd suggest using the tree from here. It includes > autonuma-based hot page promotion back to DRAM: > > http://firstname.lastname@example.org > > This is also all based on an upstream mechanism that allows > persistent memory to be onlined and used as if it were volatile: > > http://lkml.kernel.org/r/20190124231441.37A4A305@viggo.jf.intel.com > I have a high level question. Given a reclaim request for a set of nodes, if there is no demotion path out of that set, should the kernel still consider the migrations within the set of nodes? Basically should the decision to allow migrations within a reclaim request be taken at the node level or the reclaim request (or allocation level)?
next prev parent reply index Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-29 23:45 Dave Hansen 2020-06-29 23:45 ` [RFC][PATCH 1/8] mm/numa: node demotion data structure and lookup Dave Hansen 2020-06-29 23:45 ` [RFC][PATCH 2/8] mm/migrate: Defer allocating new page until needed Dave Hansen 2020-07-01 8:47 ` Greg Thelen 2020-07-01 14:46 ` Dave Hansen 2020-07-01 18:32 ` Yang Shi 2020-06-29 23:45 ` [RFC][PATCH 3/8] mm/vmscan: Attempt to migrate page in lieu of discard Dave Hansen 2020-07-01 0:47 ` David Rientjes 2020-07-01 1:29 ` Yang Shi 2020-07-01 5:41 ` David Rientjes 2020-07-01 8:54 ` Huang, Ying 2020-07-01 18:20 ` Dave Hansen 2020-07-01 19:50 ` David Rientjes 2020-07-02 1:50 ` Huang, Ying 2020-07-01 15:15 ` Dave Hansen 2020-07-01 17:21 ` Yang Shi 2020-07-01 19:45 ` David Rientjes 2020-07-02 10:02 ` Jonathan Cameron 2020-07-01 1:40 ` Huang, Ying 2020-07-01 16:48 ` Dave Hansen 2020-07-01 19:25 ` David Rientjes 2020-07-02 5:02 ` Huang, Ying 2020-06-29 23:45 ` [RFC][PATCH 4/8] mm/vmscan: add page demotion counter Dave Hansen 2020-06-29 23:45 ` [RFC][PATCH 5/8] mm/numa: automatically generate node migration order Dave Hansen 2020-06-30 8:22 ` Huang, Ying 2020-07-01 18:23 ` Dave Hansen 2020-07-02 1:20 ` Huang, Ying 2020-06-29 23:45 ` [RFC][PATCH 6/8] mm/vmscan: Consider anonymous pages without swap Dave Hansen 2020-06-29 23:45 ` [RFC][PATCH 7/8] mm/vmscan: never demote for memcg reclaim Dave Hansen 2020-06-29 23:45 ` [RFC][PATCH 8/8] mm/numa: new reclaim mode to enable reclaim-based migration Dave Hansen 2020-06-30 7:23 ` Huang, Ying 2020-06-30 17:50 ` Yang Shi 2020-07-01 0:48 ` Huang, Ying 2020-07-01 1:12 ` Yang Shi 2020-07-01 1:28 ` Huang, Ying 2020-07-01 16:02 ` Dave Hansen 2020-07-03 9:30 ` Huang, Ying 2020-06-30 18:36 ` Shakeel Butt [this message] 2020-06-30 18:51 ` [RFC][PATCH 0/8] Migrate Pages in lieu of discard Dave Hansen 2020-06-30 19:25 ` Shakeel Butt 2020-06-30 19:31 ` Dave Hansen 2020-07-01 14:24 ` [RFC] [PATCH " Zi Yan 2020-07-01 14:32 ` Dave Hansen
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