Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 8 Aug 2023 10:37:48 -0400
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Roman Gushchin <roman.gushchin@linux.dev>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
Subject: Re: [RFC v1 5/5] maple_tree: replace preallocation with slub percpu
 array prefill
Message-ID: <20230808143748.t5ravl4yaxxktikw@revolver>
Mail-Followup-To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Matthew Wilcox <willy@infradead.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Roman Gushchin <roman.gushchin@linux.dev>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
References: <20230808095342.12637-7-vbabka@suse.cz>
 <20230808095342.12637-12-vbabka@suse.cz>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230808095342.12637-12-vbabka@suse.cz>
User-Agent: NeoMutt/20220429
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?1tqPpPk1NVMeQx19AhktMxhqurzKDX+SSY6cTHq9E83UzjUHAZGflAuPLyet?=
 =?us-ascii?Q?kpjtrQ0i30292hXgbWvNw1j5v2x7vtF6YHY1RYX50WQ/PgJvLN6VE2p8Hg5/?=
 =?us-ascii?Q?XRc1H9YRPGkg61an2wJ8gmutkEJZ7HDSiNsYy7YjnitzjDfV6bGFmUdhOzHw?=
 =?us-ascii?Q?aqqNnk6tEL8t7ZcNyO01bVeAgHPDZ3asCGHemjjloQxuUqPrBuLmrXp0Hvkb?=
 =?us-ascii?Q?jgiAxfZVCQbNDR1buA/iv3cWMJmIuo5Uzu5ht77XMwcsigExSsivLa2MQi+Q?=
 =?us-ascii?Q?ykPvl86jw6rmbY7f558cVeVbktZvFwP7DCycwUYSlrhD6E7+AOMv7T1JIsB0?=
 =?us-ascii?Q?zUoSvTnlz3DUYDWhLFmCWZ4Bx1h0xJS/pPqQ6rt6Hamx96h7oBKTKVkgzvZ0?=
 =?us-ascii?Q?+swxP3JwaykLyJmqNOvzl5PDScLrhENmv7iCJKVwPSeJ/so0s+7NYTSJK4BI?=
 =?us-ascii?Q?ox2N05k0NF45ba6kmkqBJT2e/fYNtCjK1GVjG2y5Lj0O5DBBtYYCwyT2uuQZ?=
 =?us-ascii?Q?1vapoN1pD9VQBvNCdyl6AvUBROQG3xcHGeocrIHrXqPX3DcqQTp+ZD46GUhN?=
 =?us-ascii?Q?p6jFXbiYitA+Ucm+J+GZGULjBskHKDM3t9HOs8deExUen+Zvg2mVPO5P3eso?=
 =?us-ascii?Q?c3oyfQVwhdmrKwxGuSPKgppVFQVjXvzsisG9y/2ifuxwvLpk62FneUfDRUwk?=
 =?us-ascii?Q?UCNBMWhsgRmppanLJ4bH7bIgmeWNxeyEnY1hcT0PDG6kqgKAguD5BGnemsN3?=
 =?us-ascii?Q?wwelBPQDgG2kyr18D+IPGF5J0GzKfjLu7AS3cY/sIfMRbEUDGe5dKe2ds2+e?=
 =?us-ascii?Q?H4hAH8WHidHiz8h59NBa80UzJCuxKoogtSOqesDEHYuRHpU5eMn/L/cWPU3N?=
 =?us-ascii?Q?C961UdqrUyrqiJXtCzW4Jdi9DTlBtTcD1p0cH++C4VWlnOEjQHVDz48U1XSs?=
 =?us-ascii?Q?LKOVFg1mYO7Q9ppn3ap9bDmyI9mRMhiB34aJtyYqCVhh02Trpn1/eUYYgorb?=
 =?us-ascii?Q?RoBlYW/RWWTtWDH5YUlvhCYgWynL4w9ayxWbf7lQ1jS3Ndo1/nZeJAjARefx?=
 =?us-ascii?Q?woGAVZT9pnUmMUdrdoLhSFk4189Ov+h+h/xLHzJi6oTaahNJmfQ+pKV8wRc+?=
 =?us-ascii?Q?pqoOYgxssSWYtsXAPy6NYRKG34n2ceJ8B29Q3NaFPqYWefspZLTEGCXd11Br?=
 =?us-ascii?Q?UVuaRZolzlrSdoQGD4NZav9EqSIEPlRByDDFO+wErtmZYZGiwavJj2GXnazP?=
 =?us-ascii?Q?4KOm10jeZOAAs8HUxeiCUBzI85/Up++gKgVvYHdj8AJGye5mEYZhzQKN0DX7?=
 =?us-ascii?Q?W3TQo2PhiBY16IcI61xWrI/Sz82Z0Xs3cQ8v3afZGopDZVG8Qzl9RIaXDtcG?=
 =?us-ascii?Q?JTLM13Xl8PF2dZs2sOB/JVa42H1ESC4mUJzhK9CeVaxXv81/ATF6aUcNgZBR?=
 =?us-ascii?Q?xMirIRKJvHys9TcRiyZZdl8ImHrXONryJUBGU7Hr+XDMM13X7Qy7kFf4TgOr?=
 =?us-ascii?Q?e+qsgs9UnsqJDm9B17asRS6p63HvMs1wemnCTaw8amnXyjqLPVzBmtO2D2pI?=
 =?us-ascii?Q?KSuMt4lLX7YIQLnkMWLwaLoAarZ8aAit3WlvNH9F9awKFXBEUXIsWYyazYFO?=
 =?us-ascii?Q?Jw=3D=3D?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?us-ascii?Q?eqN581B1KCkwSa+EmY50aM23t7b1aVrsiRcjdbuG3FABTpTw++QXLHCEVb3x?=
 =?us-ascii?Q?PqD3CrZdQnp1vo+VSbXP+/3ZXA2lLvHTGXR5xq7SKicjvVUgbCKmFD/F6EBx?=
 =?us-ascii?Q?rPyBWRr2FhMpldotmcpSswirKHKHmBnOku3TSSe+DRzCQMGia+srNcy2mBqN?=
 =?us-ascii?Q?8w6yI1PtC6VJHJ1G2xjiVWsYzC+XUt7jcLZCpYZLES06DZu5iwcaSBO1UJo1?=
 =?us-ascii?Q?9ufBaeZ7bZiVScL/6CEZ+lkiBZKDSNJAOuwaWOzV4kNKPKlPjx+urgNdVp42?=
 =?us-ascii?Q?HhwLFH9KVQyJepWpuyJ0kaEz5Ts1kux66A2wi9nKQqsTHZmGdPLorZATAEA8?=
 =?us-ascii?Q?MrWLnwyPuysTARdN/ytYAFPPsQqWzoI9j+739Vmk9XE9qPra81u0DTHjXK5/?=
 =?us-ascii?Q?T57BdhAMOVWYSbBwaUHd8a2lQozxbbKs8J4cxOmv7O/LArdLYettspFg7KJh?=
 =?us-ascii?Q?q9Ge10YQi9p+tU2hmoTkIIj+PtfI3EV419ZrdnRJ1SaenyHIjdwC39vWHVNe?=
 =?us-ascii?Q?jFQCxbs1nZVLwfS1QMlqgLhcBFU2yXNYUgNSC7c32smHrClFTqc1uJ8gx06H?=
 =?us-ascii?Q?esuo/63tDWaAuMocj1VtGCBvhcMCdBuk7aLw0LR6OEM7H9GjFpLknc9pXVV3?=
 =?us-ascii?Q?7C6fiqKQljCpAjBGjC11XgCl57XauFmOlOpzUrRYHug8NeuW9LOJzo67Tn9R?=
 =?us-ascii?Q?1MJ8KKt+EB1/8Nw4OmBB1uLK4XtPCpMJU/Xs+6E93AadeIte71L5jCHs113q?=
 =?us-ascii?Q?yG2OVndjWy33emrlB9zoZPt8w2n8HFUyld1I3xTnZQ8C8ZwwxE1Q2K5K9Jmg?=
 =?us-ascii?Q?qNauqAMe8k+rIOtVk+UKTFfcpGHuLdBz6xY+ARrmLlh32BMa6ywFlWNsPnz2?=
 =?us-ascii?Q?GKciWRIIJDnC8R3uxvUTkV5y/vbVaW96gS8VuSchXl1mVRIRpURnLVY0FYYt?=
 =?us-ascii?Q?LgVIBOo4VM+xqdHMOx2P1jd5d3NZBKYYqFR8m4zg1/jw1rduoyL6SG19IMm/?=
 =?us-ascii?Q?U7yn27pBxzBpZ3osS7f+F9FOwRwJdJrxSLy5dNVeCHOS+DY=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 14d5e727-914b-4796-9f82-08db981d0b05
X-MS-Exchange-CrossTenant-AuthSource: SN6PR10MB3022.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Aug 2023 14:37:51.0823
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: aV8QTiw8fT61NZ3gdxgYHf82b/36EsvsXhLy15C3vgqD7a9JLfSGzMLCBQsHiX3IQD9UMWaSjUTXLboo0E7lgg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR10MB5760
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26
 definitions=2023-08-08_12,2023-08-08_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 bulkscore=0
 adultscore=0 mlxscore=0 spamscore=0 suspectscore=0 malwarescore=0
 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2306200000 definitions=main-2308080131
X-Proofpoint-GUID: ccw7EP_w3cn4AyLfQsHFNmhNJ2tJvRAy
X-Proofpoint-ORIG-GUID: ccw7EP_w3cn4AyLfQsHFNmhNJ2tJvRAy
X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE
        autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

* Vlastimil Babka <vbabka@suse.cz> [230808 05:53]:
> With the percpu array we can try not doing the preallocations in maple
> tree, and instead make sure the percpu array is prefilled, and using
> GFP_ATOMIC in places that relied on the preallocation (in case we miss
> or fail trylock on the array), i.e. mas_store_prealloc(). For now simply
> add __GFP_NOFAIL there as well.
> 
> First I tried to change mas_node_count_gfp() to not preallocate anything
> anywhere, but that lead to warns and panics, even though the other
> caller mas_node_count() uses GFP_NOWAIT | __GFP_NOWARN so it has no
> guarantees... So I changed just mas_preallocate(). I let it still to
> truly preallocate a single node, but maybe it's not necessary?

Ah, yes.  I added a check to make sure we didn't allocate more nodes
when using preallocations.  This check is what you are hitting when you
don't allocate anything.  This is tracked in mas_flags by
setting/clearing MA_STATE_PREALLOC.  Good news, that check works!

> ---
>  lib/maple_tree.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 7a8e7c467d7c..5a209d88c318 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -5534,7 +5534,12 @@ void mas_store_prealloc(struct ma_state *mas, void *entry)
>  
>  	mas_wr_store_setup(&wr_mas);
>  	trace_ma_write(__func__, mas, 0, entry);
> +
> +retry:
>  	mas_wr_store_entry(&wr_mas);
> +	if (unlikely(mas_nomem(mas, GFP_ATOMIC | __GFP_NOFAIL)))
> +		goto retry;
> +
>  	MAS_WR_BUG_ON(&wr_mas, mas_is_err(mas));
>  	mas_destroy(mas);
>  }
> @@ -5550,9 +5555,10 @@ EXPORT_SYMBOL_GPL(mas_store_prealloc);
>  int mas_preallocate(struct ma_state *mas, gfp_t gfp)
>  {
>  	int ret;
> +	int count = 1 + mas_mt_height(mas) * 3;
>  
> -	mas_node_count_gfp(mas, 1 + mas_mt_height(mas) * 3, gfp);
> -	mas->mas_flags |= MA_STATE_PREALLOC;
> +	mas_node_count_gfp(mas, 1, gfp);
> +	kmem_cache_prefill_percpu_array(maple_node_cache, count, gfp);
>  	if (likely(!mas_is_err(mas)))
>  		return 0;
>  
> -- 
> 2.41.0
>