From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92708C433DF for ; Wed, 20 May 2020 18:27:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5857C20671 for ; Wed, 20 May 2020 18:27:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="P3/+t99s" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5857C20671 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9562F8000B; Wed, 20 May 2020 14:27:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 905318000A; Wed, 20 May 2020 14:27:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 781258000B; Wed, 20 May 2020 14:27:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0082.hostedemail.com [216.40.44.82]) by kanga.kvack.org (Postfix) with ESMTP id 4333F8000A for ; Wed, 20 May 2020 14:27:45 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id DC6F08248047 for ; Wed, 20 May 2020 18:27:44 +0000 (UTC) X-FDA: 76837930890.04.heat55_26584fdac9d13 X-HE-Tag: heat55_26584fdac9d13 X-Filterd-Recvd-Size: 7676 Received: from userp2120.oracle.com (userp2120.oracle.com [156.151.31.85]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Wed, 20 May 2020 18:27:43 +0000 (UTC) Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04KIHSQi000794; Wed, 20 May 2020 18:27:11 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=corp-2020-01-29; bh=+I5DK1bpDxPp17bxmkq3TLU7ktjAi9yJhHWfSrepooM=; b=P3/+t99sOI/cJLLQGLPGcYunKHfgTXLhGsWaI52GKYtr7wyKIO64OoVtL9IMpVjD74uS r8CzhtQuf1c1Jitqjbj9kH5cupw6vHmbuWRRgEHEQH8ZJbs/tLe6xx+nXDL1BwAvlD+F R8R3Xyx8Gex8EBS0uet5gInYKJlSgBY6zWUTNHfldY+mT6Dw5c9Ka5098MbyD8WMf03L /NJHzNYzKCc3WLNcSBYOArsURzvhCgY67wjBxEMWNQzJS7WpLdmCbw7EOK31zOgdiR92 ml56VbjMyyzFqVbE3KSAyqwxek3U/YkOCY6ZY3BUAFQTuKQdK9He5gQ9z+lw066FZ3b8 5Q== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 31501rb8a9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 20 May 2020 18:27:11 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04KIDD4p076208; Wed, 20 May 2020 18:27:11 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 315020rdjx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 May 2020 18:27:10 +0000 Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 04KIR8V3008161; Wed, 20 May 2020 18:27:08 GMT Received: from localhost.localdomain (/98.229.125.203) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 20 May 2020 11:27:08 -0700 From: Daniel Jordan To: Andrew Morton , Herbert Xu , Steffen Klassert Cc: Alex Williamson , Alexander Duyck , Dan Williams , Dave Hansen , David Hildenbrand , Jason Gunthorpe , Jonathan Corbet , Josh Triplett , Kirill Tkhai , Michal Hocko , Pavel Machek , Pavel Tatashin , Peter Zijlstra , Randy Dunlap , Robert Elliott , Shile Zhang , Steven Sistare , Tejun Heo , Zi Yan , linux-crypto@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Daniel Jordan Subject: [PATCH v2 7/7] padata: document multithreaded jobs Date: Wed, 20 May 2020 14:26:45 -0400 Message-Id: <20200520182645.1658949-8-daniel.m.jordan@oracle.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200520182645.1658949-1-daniel.m.jordan@oracle.com> References: <20200520182645.1658949-1-daniel.m.jordan@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9627 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 bulkscore=0 suspectscore=0 phishscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005200148 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9627 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 spamscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 cotscore=-2147483648 impostorscore=0 bulkscore=0 adultscore=0 malwarescore=0 phishscore=0 mlxscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005200148 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Add Documentation for multithreaded jobs. Signed-off-by: Daniel Jordan --- Documentation/core-api/padata.rst | 41 +++++++++++++++++++++++-------- 1 file changed, 31 insertions(+), 10 deletions(-) diff --git a/Documentation/core-api/padata.rst b/Documentation/core-api/p= adata.rst index 9a24c111781d9..b7e047af993e8 100644 --- a/Documentation/core-api/padata.rst +++ b/Documentation/core-api/padata.rst @@ -4,23 +4,26 @@ The padata parallel execution mechanism =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 -:Date: December 2019 +:Date: April 2020 =20 Padata is a mechanism by which the kernel can farm jobs out to be done i= n -parallel on multiple CPUs while retaining their ordering. It was develo= ped for -use with the IPsec code, which needs to be able to perform encryption an= d -decryption on large numbers of packets without reordering those packets.= The -crypto developers made a point of writing padata in a sufficiently gener= al -fashion that it could be put to other uses as well. +parallel on multiple CPUs while optionally retaining their ordering. =20 -Usage -=3D=3D=3D=3D=3D +It was originally developed for IPsec, which needs to perform encryption= and +decryption on large numbers of packets without reordering those packets.= This +is currently the sole consumer of padata's serialized job support. + +Padata also supports multithreaded jobs, splitting up the job evenly whi= le load +balancing and coordinating between threads. + +Running Serialized Jobs +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 Initializing ------------ =20 -The first step in using padata is to set up a padata_instance structure = for -overall control of how jobs are to be run:: +The first step in using padata to run parallel jobs is to set up a +padata_instance structure for overall control of how jobs are to be run:= : =20 #include =20 @@ -162,6 +165,24 @@ functions that correspond to the allocation in rever= se:: It is the user's responsibility to ensure all outstanding jobs are compl= ete before any of the above are called. =20 +Running Multithreaded Jobs +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D + +A multithreaded job has a main thread and zero or more helper threads, w= ith the +main thread participating in the job and then waiting until all helpers = have +finished. padata splits the job into units called chunks, where a chunk= is a +piece of the job that one thread completes in one call to the thread fun= ction. + +A user has to do three things to run a multithreaded job. First, descri= be the +job by defining a padata_mt_job structure, which is explained in the Int= erface +section. This includes a pointer to the thread function, which padata w= ill +call each time it assigns a job chunk to a thread. Then, define the thr= ead +function, which accepts three arguments, ``start``, ``end``, and ``arg``= , where +the first two delimit the range that the thread operates on and the last= is a +pointer to the job's shared state, if any. Prepare the shared state, wh= ich is +typically a stack-allocated structure that wraps the required data. Las= t, call +padata_do_multithreaded(), which will return once the job is finished. + Interface =3D=3D=3D=3D=3D=3D=3D=3D=3D =20 --=20 2.26.2