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Wed, 17 Jul 2019 18:13:00 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x6HI7gEr177982; Wed, 17 Jul 2019 18:13:00 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 2tt77h9p5d-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 17 Jul 2019 18:13:00 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x6HICvFC007838; Wed, 17 Jul 2019 18:12:59 GMT Received: from anon-dhcp-171.1015granger.net (/68.61.232.219) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 17 Jul 2019 18:12:57 +0000 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: [PATCH 1/2] SUNRPC: Fix up backchannel slot table accounting From: Chuck Lever In-Reply-To: <97e9839faef3d1bc901d4ced3d0cf2e0bf2a0bd1.camel@hammerspace.com> Date: Wed, 17 Jul 2019 14:12:56 -0400 Cc: Linux NFS Mailing List Content-Transfer-Encoding: quoted-printable Message-Id: References: <20190716200157.38583-1-trond.myklebust@hammerspace.com> <99A569FB-DD7F-4547-AB06-FEB5DABA8488@oracle.com> <97e9839faef3d1bc901d4ced3d0cf2e0bf2a0bd1.camel@hammerspace.com> To: Trond Myklebust X-Mailer: Apple Mail (2.3445.104.11) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9321 signatures=668688 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907170208 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9321 signatures=668688 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907170208 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org > On Jul 17, 2019, at 1:19 PM, Trond Myklebust = wrote: >=20 > On Wed, 2019-07-17 at 09:55 -0400, Chuck Lever wrote: >> Hi Trond- >>=20 >>> On Jul 16, 2019, at 4:01 PM, Trond Myklebust >>> wrote: >>>=20 >>> Add a per-transport maximum limit in the socket case, and add >>> helpers to allow the NFSv4 code to discover that limit. >>=20 >> For RDMA, the number of credits is permitted to change during the >> life >> of the connection, so this is not a fixed limit for such transports. >=20 > This is defining a maximum value, which is used for backchannel = session > slot negotiation. >=20 >>=20 >> And, AFAICT, it's not necessary to know the transport's limit. The >> lesser of the NFS backchannel and RPC/RDMA reverse credit limit will >> be used. >=20 > The server needs to know how many requests it can send in parallel on > the back channel. If it sends too many, which it can and will do on > TCP, then we currently break the connection, and so callbacks end up > being dropped or missed altogether. IIUC, RPC/RDMA has a fixed maximum constant. Would you like a patch at some point that advertises that constant via ->bc_num_slots ? -- Chuck Lever