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From: Roman Gushchin <guro@fb.com>
To: "Tobin C. Harding" <tobin@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Alexander Viro <viro@ftp.linux.org.uk>,
	"Christoph Hellwig" <hch@infradead.org>,
	Pekka Enberg <penberg@cs.helsinki.fi>,
	"David Rientjes" <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Christopher Lameter <cl@linux.com>,
	Miklos Szeredi <mszeredi@redhat.com>,
	Andreas Dilger <adilger@dilger.ca>,
	Waiman Long <longman@redhat.com>,
	"Tycho Andersen" <tycho@tycho.ws>, Theodore Ts'o <tytso@mit.edu>,
	Andi Kleen <ak@linux.intel.com>,
	David Chinner <david@fromorbit.com>,
	Nick Piggin <npiggin@gmail.com>, Rik van Riel <riel@redhat.com>,
	Hugh Dickins <hughd@google.com>, Jonathan Corbet <corbet@lwn.net>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v5 13/16] slub: Enable balancing slabs across nodes
Date: Tue, 21 May 2019 01:04:10 +0000	[thread overview]
Message-ID: <20190521010404.GB9552@tower.DHCP.thefacebook.com> (raw)
In-Reply-To: <20190520054017.32299-14-tobin@kernel.org>

On Mon, May 20, 2019 at 03:40:14PM +1000, Tobin C. Harding wrote:
> We have just implemented Slab Movable Objects (SMO).  On NUMA systems
> slabs can become unbalanced i.e. many slabs on one node while other
> nodes have few slabs.  Using SMO we can balance the slabs across all
> the nodes.
> 
> The algorithm used is as follows:
> 
>  1. Move all objects to node 0 (this has the effect of defragmenting the
>     cache).

This already sounds dangerous (or costly). Can't it be done without
cross-node data moves?

> 
>  2. Calculate the desired number of slabs for each node (this is done
>     using the approximation nr_slabs / nr_nodes).

So that on this step only (actual data size - desired data size) has
to be moved?

Thanks!

  reply	other threads:[~2019-05-21  1:05 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20  5:40 [RFC PATCH v5 00/16] Slab Movable Objects (SMO) Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 01/16] slub: Add isolate() and migrate() methods Tobin C. Harding
2019-05-21  0:37   ` Roman Gushchin
2019-05-20  5:40 ` [RFC PATCH v5 02/16] tools/vm/slabinfo: Add support for -C and -M options Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 03/16] slub: Sort slab cache list Tobin C. Harding
2019-05-21  0:38   ` Roman Gushchin
2019-05-20  5:40 ` [RFC PATCH v5 04/16] slub: Slab defrag core Tobin C. Harding
2019-05-21  0:51   ` Roman Gushchin
2019-05-21  1:15     ` Tobin C. Harding
2019-05-21  1:25       ` Roman Gushchin
2019-05-20  5:40 ` [RFC PATCH v5 05/16] tools/vm/slabinfo: Add remote node defrag ratio output Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 06/16] tools/vm/slabinfo: Add defrag_used_ratio output Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 07/16] tools/testing/slab: Add object migration test module Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 08/16] tools/testing/slab: Add object migration test suite Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 09/16] lib: Separate radix_tree_node and xa_node slab cache Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 10/16] xarray: Implement migration function for xa_node objects Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 11/16] tools/testing/slab: Add XArray movable objects tests Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 12/16] slub: Enable moving objects to/from specific nodes Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 13/16] slub: Enable balancing slabs across nodes Tobin C. Harding
2019-05-21  1:04   ` Roman Gushchin [this message]
2019-05-21  1:44     ` Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 14/16] dcache: Provide a dentry constructor Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 15/16] dcache: Implement partial shrink via Slab Movable Objects Tobin C. Harding
2019-05-20  5:40 ` [RFC PATCH v5 16/16] dcache: Add CONFIG_DCACHE_SMO Tobin C. Harding
2019-05-21  0:57   ` Roman Gushchin
2019-05-21  1:31     ` Tobin C. Harding
2019-05-21  2:05       ` Roman Gushchin
2019-05-21  3:15         ` Tobin C. Harding
2019-05-29  3:54         ` Tobin C. Harding
2019-05-29 16:16           ` Roman Gushchin
2019-06-03  4:26             ` Tobin C. Harding
2019-06-03 20:34               ` Roman Gushchin

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