Hi Dariusz, > -----Original Message----- > From: Stojaczyk, DariuszX > Sent: Friday, March 2, 2018 6:41 AM > To: dev@dpdk.org; Tan, Jianfeng; Maxime Coquelin; Burakov, Anatoly; > Yuanhan Liu > Cc: Harris, James R; Thomas Monjalon > Subject: virtio with 2MB hugepages - bringing back single file segments > > Hi, > > I'm trying to make a vhost-user initiator built upon DPDK work with 2MB > hugepages. In the initiator we have to share all memory with the host > process, so it > can perform DMA. DPDK currently enforces having one descriptor per > hugepage and there's an artificial limit of shared descriptors in DPDK vhost- > user implementation (currently 8). Because of that, all DPDK vhost-user > initiators are practically limited to 1GB hugepages at the moment. We can > always increase the artificial descriptor limit, but then we're limited by > sendmsg() itself, which on Linux accepts no more than 253 descriptors. > However, could we increase the vhost-user implementation limit to - say - > 128, and bring back "single file segments" [1]?
"Single file segments [1]" can help at the scenario that 2MB hugepages are not too scatter; i.e., some pages are physically contiguous. But it cannot solve the issue completely (imagine the worst situation). Plus, it makes the memory part a little complex. So we are expecting it (with some other issues on memory part) being addressed completely by Anatoly's rework on memory. Thanks, Jianfeng
