Re: Question on RDMA atomic operations
From: Asgeir Eiriksson <hidden>
Date: 2016-08-25 21:11:13
Hello Dong, The ordering rules for iWARP RDMA are spelled out in RFC7306 (see https://tools.ietf.org/pdf/rfc7306.pdf section 5, pp. 24 for the two ordering cases you asked about) and RFC5040 has the rest of the iWARP RDMA ordering rules The answer to your question is the same for iWARP RDMA as that provided by Majd for IB Regards, ‘Asgeir
On Aug 25, 2016, at 12:11 AM, Majd Dibbiny [off-list ref] wrote:quoted
On Aug 24, 2016, at 11:43 PM, Dong Young Yoon [off-list ref] wrote: Hi, My name is Dong Young and I am a PhD student at the University of Michigan. Recently, we have been working on a research topic related to RDMA and had an observation where there is a race condition between RDMA atomic operations (e.g., fetch-and-add) and RDMA 1-sided writes. We would like to verity whether what we observed is actually true (i.e., no atomicity guaranteed between RDMA atomic operation and RDMA read/write).Hi Dong, If you post an atomic operation followed by RDMA read/write, you need a fence between the two, because the second one might start processing before the first one has completed processing. In order to do that, you need to set the IBV_SEND_FENCE in the send_flags of the wr.quoted
Is it really true? I have also contacted other fellow researchers who worked on RDMA, but they do not seem to be 100% sure on this matter. Thank you so much in advance for your help. Thanks, Dong Young-- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html-- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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