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Date: Fri, 22 Mar 2019 11:47:43 -0500 From: Bjorn Helgaas <helgaas@...nel.org> To: Logan Gunthorpe <logang@...tatee.com> Cc: linux-kernel@...r.kernel.org, linux-ntb@...glegroups.com, linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org, Jon Mason <jdmason@...zu.us>, Joerg Roedel <joro@...tes.org>, Allen Hubbe <allenbh@...il.com>, Dave Jiang <dave.jiang@...el.com>, Serge Semin <fancer.lancer@...il.com>, Eric Pilmore <epilmore@...aio.com> Subject: Re: [PATCH v3 09/10] NTB: Add MSI interrupt support to ntb_transport Hi Logan, Drive-by nits: On Thu, Mar 21, 2019 at 06:06:44PM -0600, Logan Gunthorpe wrote: > Introduce the module parameter 'use_msi' which, when set uses s/set/set,/ > MSI interrupts instead of doorbells for each queue pair (QP). T > he parameter is only available if NTB MSI support is configured into Spurious newline in the middle of "The". > the kernel. We also require there to be more than one memory window > (MW) so that an extra one is available to forward the APIC region. > > To use MSIs, we request one interrupt per QP and forward the MSI address > and data to the peer using scratch pad registers (SPADS) above the MW > spads. (If there are not enough SPADS the MSI interrupt will not be used.) /spads/SPADS/ for consistency > Once registered, we simply use ntb_msi_peer_trigger and the recieving s/recieving/receiving/ > ISR simply queues up the rxc_db_work for the queue. > > This addition can significantly improve performance of ntb_transport. > In a simple, untuned, apples-to-apples comparision using ntb_netdev > and iperf with switchtec hardware, I see 3.88Gb/s without MSI > interrupts and 14.1Gb/s which is a more than 3x improvement. s/which is/with MSI, which is/ Bjorn
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