Received-SPF: pass (google.com: domain of linux-kernel+bounces-84050-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Tue, 27 Feb 2024 16:26:39 -0500
From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Gang Li <gang.li@linux.dev>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        Jane Chu <jane.chu@oracle.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, ligang.bdlg@bytedance.com
Subject: Re: [PATCH v6 5/8] padata: downgrade padata_do_multithreaded to
 serial execution for non-SMP
Message-ID: <e44cv3c7lafc2a5p4wkhxjaipq4hgclzuceignzzp37kl4l2pj@t7bgio7s7p4q>
References: <20240222140422.393911-1-gang.li@linux.dev>
 <20240222140422.393911-6-gang.li@linux.dev>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240222140422.393911-6-gang.li@linux.dev>
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: 
	=?us-ascii?Q?vihJOUquaBpNexnrF3Zipa8IDEP4WOwNjrEci9yKOjy5FbRgsiKczj5APh8J?=
 =?us-ascii?Q?ZHzCdcqHnXN9p0l4moA/WRssUQRYZAQ7eqvfnc8a5kgMY5hgVfQGp1u455EZ?=
 =?us-ascii?Q?5A0WSTqraX78JXV8tOYkVfHUkN6b1WCbFKG4QOr30zH9ESrPFiLqoilI05fv?=
 =?us-ascii?Q?cOiZiYwo/y0qcHTHjuptfXkKoqwPbIqIY8JXo+vj1tdiEUcCNAYGq77PoaOb?=
 =?us-ascii?Q?cjYvXsm7KKnNfH6snbS6jX11Bh1ABbdRz00SNf6ABz6dF1vNXY/JnldUAxbK?=
 =?us-ascii?Q?WGE/dcAlcyD3zkyrkjluzZ5054GZVyC8Sx6CUyfiJ300lrQYSUnlh5Z/pnTw?=
 =?us-ascii?Q?a4AtrxnyWBApVHhkfDQh5C8FqS5ixNSug0fCuTaCGxIJrAvohxAD5ztKzYLD?=
 =?us-ascii?Q?223M5zM45tu2TtpGt6jK90LaFRXptH2enDmpuUZ6AI2k7cSMcvvK7iqqI1+0?=
 =?us-ascii?Q?zW31DQFwjRwvaImxL4/31YW9P1qxC9FZTSZnxLOgrrwo0SIVbESJB4MeW7BU?=
 =?us-ascii?Q?9zWVdJR1ZwPsoGnp7RCSEoR5G47B3UAyV/YCbSvJPAekRqKDhBj8jnaKoNsk?=
 =?us-ascii?Q?vLQfIVAK8IC2dAfRV41FPtyPNbDRnaUXq05EatPmTBuCEUtfxLMWfz3Zdub1?=
 =?us-ascii?Q?836GbwYzu2bC8gDPZMeM/LV5+RVZKbENiCWwssz9+cVDuXfdaY/xRmtooZpS?=
 =?us-ascii?Q?MnD927r7IqVIhVzSSoQnkxlOjK7+Usb1qikPtP3c+DY8QTsBYEewUXmcR+ec?=
 =?us-ascii?Q?aQwrh/78dpCrtsaVXxXGUOKkJ2c0Dy2dRGtsrOHPiwoDF9q/i5juraG8H2Rq?=
 =?us-ascii?Q?QjQnbLFJHvTLDDezd5sL1y48o+4SatXBQrNtYmxQG2lYEB/U3fBdVNChNKRT?=
 =?us-ascii?Q?gmPM1dyyyf+O/KmPa4jiXtrvdjRRplcd/JUrJe76hy/l4buMSP9toePsWaM8?=
 =?us-ascii?Q?BGjwvIVayIKoc6rCBzxZ1wzGMpDDwG/3dHwNOQ8iqt/aWyTjlDMQqu/OJ39h?=
 =?us-ascii?Q?MYaH/6WYqfXtVvxUKHAvUnJhvguaO6fiRDpSmL5m3i/tpOh/rfVVd+7OtOv1?=
 =?us-ascii?Q?okXeWmZIJuw+0Qo2eIj8TRPd3xLYAKdBV4Re7T8gcae9ktpzWE4dqKQh5tbA?=
 =?us-ascii?Q?WZtnncYeF59QfDxuzxdFwHwPvaB+kpkxB0M957gsH9jSHiNr14OvafqgWTDy?=
 =?us-ascii?Q?rTwnbQpi9CkebRNbQsvcqKocTOxeDZC7kQnvzt+ARi371tJzAEm9vDEGXkd/?=
 =?us-ascii?Q?6Nzrx8n62Tk/xu8T6mitQyrwOMaqOlMfkfvT6cJR/OGjVcVTXnInjo24HPUj?=
 =?us-ascii?Q?APbuDCQw/tVCGFAyafZO89a5+DiEUBZAPa3pgC7iMdxpqR4wuKXnvJ8CMcy3?=
 =?us-ascii?Q?/1ZG3VpwcVtjoLVUiTI1TGMJkXSTSb+FWbMdKzuvEiwzj8dY7uP/65bEydy8?=
 =?us-ascii?Q?TIjBO8Vskv56eiMvYQQnOmoCZgDPHGC2/7pp3VndEqJ7BpF1VqGCyIiOKSru?=
 =?us-ascii?Q?TzM7HBLYlifwnT6VKSqjZ08ydUeYx1AkKkNOoItxGSCQSh7QR3pUUiVvNniX?=
 =?us-ascii?Q?MNGtzY3tiFPZ3NzvRGpi+fBuqIMrfkFZHhEgVbux0q1kizc0kIVfuLCdubZ/?=
 =?us-ascii?Q?UQ=3D=3D?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 
	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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: fe05a9f5-28b2-4757-4b6b-08dc37daca8d
X-MS-Exchange-CrossTenant-AuthSource: SA1PR10MB5711.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Feb 2024 21:26:42.1958
 (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: iyOG72du24LNyq7qP2FevwV2iLsdt1gaOJmZ2qa7ZcBuaMdw3c6mlfCCUJMgFkFi5BYFu+6nYdHNg3ewatkcxK4zq54S3CVhXSRxVlOK67A=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BLAPR10MB4961
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26
 definitions=2024-02-27_09,2024-02-27_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 bulkscore=0
 mlxlogscore=999 malwarescore=0 phishscore=0 mlxscore=0 suspectscore=0
 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2311290000 definitions=main-2402270164
X-Proofpoint-GUID: ILH-E7pJbBaIXxcYh0IZd9xbmaeKLwmd
X-Proofpoint-ORIG-GUID: ILH-E7pJbBaIXxcYh0IZd9xbmaeKLwmd

On Thu, Feb 22, 2024 at 10:04:18PM +0800, Gang Li wrote:
> hugetlb parallelization depends on PADATA, and PADATA depends on SMP.
> 
> PADATA consists of two distinct functionality: One part is
> padata_do_multithreaded which disregards order and simply divides
> tasks into several groups for parallel execution. Hugetlb
> init parallelization depends on padata_do_multithreaded.
> 
> The other part is composed of a set of APIs that, while handling data in
> an out-of-order parallel manner, can eventually return the data with
> ordered sequence. Currently Only `crypto/pcrypt.c` use them.
> 
> All users of PADATA of non-SMP case currently only use
> padata_do_multithreaded. It is easy to implement a serial one in
> include/linux/padata.h. And it is not necessary to implement another
> functionality unless the only user of crypto/pcrypt.c does not depend on
> SMP in the future.
> 
> Signed-off-by: Gang Li <ligang.bdlg@bytedance.com>
> Tested-by: Paul E. McKenney <paulmck@kernel.org>
> ---
>  include/linux/padata.h | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/padata.h b/include/linux/padata.h
> index 8f418711351bc..0146daf344306 100644
> --- a/include/linux/padata.h
> +++ b/include/linux/padata.h
> @@ -180,10 +180,6 @@ struct padata_instance {
>  
>  #ifdef CONFIG_PADATA
>  extern void __init padata_init(void);
> -#else
> -static inline void __init padata_init(void) {}
> -#endif
> -
>  extern struct padata_instance *padata_alloc(const char *name);
>  extern void padata_free(struct padata_instance *pinst);
>  extern struct padata_shell *padata_alloc_shell(struct padata_instance *pinst);
> @@ -194,4 +190,12 @@ extern void padata_do_serial(struct padata_priv *padata);
>  extern void __init padata_do_multithreaded(struct padata_mt_job *job);
>  extern int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
>  			      cpumask_var_t cpumask);
> +#else
> +static inline void __init padata_init(void) {}
> +static inline void __init padata_do_multithreaded(struct padata_mt_job *job)
> +{

An early return here for zero-sized jobs is consistent with the
CONFIG_PADATA version and avoids hugetlb_pages_alloc_boot taking a lock
and flushing the tlb when there's no work to do.

With that,

Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>

> +	job->thread_fn(job->start, job->start + job->size, job->fn_arg);
> +}
> +#endif
> +
>  #endif
> -- 
> 2.20.1
>