On 7/16/2015 6:25 PM, Bart Van Assche wrote:
Hello,
Hi Bart, I agree it would definitely help as the lack of immediate data emphasizes the additional latency of doing rdma reads.
As you probably know for write requests "immediate data" means sending the data in the same packet as the write command instead of sending it as a separate packet. This approach improves performance and reduces latency. Although support for immediate data has not been standardized,
Has anyone tried to get it into the standard? It would seem beneficial to just add it. I wouldn't want this to be a Linux compatible only feature...
it is easy to add to the SRP initiator and target drivers. Implementations exist in the ib_srp-backport initiator driver and the SCST SRP target driver (see also https://github.com/bvanassche/ib_srp-backport and http://sourceforge.net/p/scst/svn/HEAD/tree/trunk/srpt/). These implementations are available since considerable time, work reliably, are backwards compatible and support zero-copy. Since using immediate data provides a measurable performance improvement I'm wondering whether it would be acceptable to add support for immediate data to the SRP drivers in the Linux kernel tree (ib_srp and ib_srpt) ?
Was this tested against any other array besides SCST and LIO? I know people are using SRP against various arrays (Oracle ZFS, RamSan TMS, DDN Fusion, NIMBUS, NetApp E5400A...). Their not running upstream kernels, but they will catch up at some point... Sagi. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
