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Wythe" , Tony Lu , David Miller , Jakub Kicinski , Eric Dumazet , Paolo Abeni , netdev@vger.kernel.org, linux-s390@vger.kernel.org, Heiko Carstens , Jan Karcher , Gerd Bayer , Alexandra Winter , Nils Hoppmann , Niklas Schnell , Thorsten Winkler , Karsten Graul , Stefan Raspl , Halil Pasic Subject: Re: [PATCH net-next] net/smc: increase SMC_WR_BUF_CNT Message-ID: <20241104174215.130784ee.pasic@linux.ibm.com> In-Reply-To: <20241031133017.682be72b.pasic@linux.ibm.com> References: <20241025074619.59864-1-wenjia@linux.ibm.com> <20241025235839.GD36583@linux.alibaba.com> <20241031133017.682be72b.pasic@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: KKJemEDYMel8fChJpvLQZAfhttD1aN1I X-Proofpoint-ORIG-GUID: h_bJPmKXLraQZfF1yiYE2828jM_WmhM- X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 mlxscore=0 phishscore=0 bulkscore=0 clxscore=1015 impostorscore=0 priorityscore=1501 malwarescore=0 mlxlogscore=999 lowpriorityscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2411040140 On Thu, 31 Oct 2024 13:30:17 +0100 Halil Pasic wrote: > On Sat, 26 Oct 2024 07:58:39 +0800 > Dust Li wrote: > > > >For some reason include/linux/wait.h does not offer a top level wrapper > > >macro for wait_event with interruptible, exclusive and timeout. I did > > >not spend too many cycles on thinking if that is even a combination that > > >makes sense (on the quick I don't see why not) and conversely I > > >refrained from making an attempt to accomplish the interruptible, > > >exclusive and timeout combo by using the abstraction-wise lower > > >level __wait_event interface. > > > > > >To alleviate the tx performance bottleneck and the CPU overhead due to > > >the spinlock contention, let us increase SMC_WR_BUF_CNT to 256. > > > > Hi, > > > > Have you tested other values, such as 64? In our internal version, we > > have used 64 for some time. > > Yes we have, but I'm not sure the data is still to be found. Let me do > some digging. > We did some digging and according to that data 64 is not likely to cut it on the TX end for highly parallel request-response workload. But we will measure some more these days just to be on the safe side. > > > > Increasing this to 256 will require a 36K continuous physical memory > > allocation in smc_wr_alloc_link_mem(). Based on my experience, this may > > fail on servers that have been running for a long time and have > > fragmented memory. > > Good point! It is possible that I did not give sufficient thought to > this aspect. > The failing allocation would lead to a fallback to TCP I believe. Which I don't consider a catastrophic failure. But let us put this patch on hold and see if we can come up with something better. Regards, Halil