> -----Original Message----- > From: Michael S. Tsirkin [mailto:[email protected]] > Sent: Thursday, May 02, 2013 04:56 > To: Or Gerlitz > Cc: Roland Dreier; [email protected]; Yan Burman; linux- > [email protected] > Subject: Re: decent performance drop for SCSI LLD / SAN initiator when > iommu is turned on > > On Thu, May 02, 2013 at 02:11:15AM +0300, Or Gerlitz wrote: > > Hi Roland, IOMMU folks, > > > > So we've noted that when configuring the kernel && booting with intel > > iommu set to on on a physical node (non VM, and without enabling SRIOV > > by the HW device driver) raw performance of the iSER (iSCSI RDMA) SAN > > initiator is reduced notably, e.g in the testbed we looked today we > > had ~260K 1KB random IOPS and 5.5GBs BW for 128KB IOs with iommu > > turned off for single LUN, and ~150K IOPS and 4GBs BW with iommu > > turned on. No change on the target node between runs. > > That's why we have iommu=pt. > See definition of iommu_pass_through in arch/x86/kernel/pci-dma.c.
I tried passing "intel_iommu=on iommu=pt" to 3.8.11 kernel and I still get performance degradation. I get the same numbers with iommu=pt as without it. I wanted to send perf output, but currently I seem to have some problem with its output. Will try to get perf differences next week. Yan -- 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
