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Re: [PATCH 00/31] Move LRU page reclaim from zones to nodes v8

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On Fri, Jul 08, 2016 at 09:27:13AM +1000, Dave Chinner wrote:
> .....
> > This series is not without its hazards. There are at least three areas
> > that I'm concerned with even though I could not reproduce any problems in
> > that area.
> > 
> > 1. Reclaim/compaction is going to be affected because the amount of reclaim is
> >    no longer targetted at a specific zone. Compaction works on a per-zone basis
> >    so there is no guarantee that reclaiming a few THP's worth page pages will
> >    have a positive impact on compaction success rates.
> > 
> > 2. The Slab/LRU reclaim ratio is affected because the frequency the shrinkers
> >    are called is now different. This may or may not be a problem but if it
> >    is, it'll be because shrinkers are not called enough and some balancing
> >    is required.
> 
> Given that XFS has a much more complex set of shrinkers and has a
> much more finely tuned balancing between LRU and shrinker reclaim,
> I'd be interested to see if you get the same results on XFS for the
> tests you ran on ext4. It might also be worth running some highly
> concurrent inode cache benchmarks (e.g. the 50-million inode, 16-way
> concurrent fsmark tests) to see what impact heavy slab cache
> pressure has on shrinker behaviour and system balance...
> 

I had tested XFS with earlier releases and noticed no major problems
so later releases tested only one filesystem.  Given the changes since,
a retest is desirable. I've posted the current version of the series but
I'll queue the tests to run over the weekend. They are quite time consuming
to run unfortunately.

On the fsmark configuration, I configured the test to use 4K files
instead of 0-sized files that normally would be used to stress inode
creation/deletion. This is to have a mix of page cache and slab
allocations. Shout if this does not suit your expectations.

Finally, not all the machines I'm using can store 50 million inodes
of this size. The benchmark has been configured to use as many inodes
as it estimates will fit in the disk. In all cases, it'll exert memory
pressure. Unfortunately, the storage is simple so there is no guarantee
it'll find all problems but that's standard unfortunately.

Thanks.

-- 
Mel Gorman
SUSE Labs

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[PATCH 00/31] Move LRU page reclaim from zones to nodes v8 Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 06/31] mm, vmscan: make kswapd reclaim in terms of nodes Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 09/31] mm, vmscan: by default have direct reclaim only shrink once per node Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 10/31] mm, vmscan: remove duplicate logic clearing node congestion and dirty state Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 07/31] mm, vmscan: remove balance gap Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 02/31] mm, vmscan: move lru_lock to the node Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 05/31] mm, vmscan: have kswapd only scan based on the highest requested zone Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:40 +0200
  [PATCH 19/31] mm: move vmscan writes and file write accounting to the node Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 17/31] mm: rename NR_ANON_PAGES to NR_ANON_MAPPED Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 30/31] mm, vmstat: print node-based stats in zoneinfo file Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 31/31] mm, vmstat: Remove zone and node double accounting by approximating retries Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 22/31] mm: convert zone_reclaim to node_reclaim Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 26/31] mm, page_alloc: remove fair zone allocation policy Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 28/31] mm: vmstat: replace __count_zone_vm_events with a zone id equivalent Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 21/31] mm, page_alloc: Wake kswapd based on the highest eligible zone Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 20/31] mm, vmscan: only wakeup kswapd once per node for the requested classzone Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 14/31] mm, workingset: make working set detection node-aware Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 18/31] mm: move most file-based accounting to the node Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 23/31] mm, vmscan: Avoid passing in classzone_idx unnecessarily to shrink_node Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 27/31] mm: page_alloc: cache the last node whose dirty limit is reached Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 11/31] mm: vmscan: do not reclaim from kswapd if there is any eligible zone Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 12/31] mm, vmscan: make shrink_node decisions more node-centric Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 15/31] mm, page_alloc: consider dirtyable memory in terms of nodes Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 24/31] mm, vmscan: Avoid passing in classzone_idx unnecessarily to compaction_ready Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 13/31] mm, memcg: move memcg limit enforcement from zones to nodes Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 25/31] mm, vmscan: add classzone information to tracepoints Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 29/31] mm: vmstat: account per-zone stalls and pages skipped during reclaim Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  [PATCH 16/31] mm: move page mapped accounting to the node Mel Gorman <mgorman@techsingularity.net> - 2016-07-01 17:50 +0200
  Re: [PATCH 00/31] Move LRU page reclaim from zones to nodes v8 Dave Chinner <david@fromorbit.com> - 2016-07-08 01:30 +0200
    Re: [PATCH 00/31] Move LRU page reclaim from zones to nodes v8 Mel Gorman <mgorman@techsingularity.net> - 2016-07-08 12:00 +0200

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