From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Grover Subject: is it possible to avoid syncing after an rdma write? Date: Tue, 16 Feb 2010 15:29:48 -0800 Message-ID: <4B7B2A6C.80101@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org Right now, RDS follows each RDMA write op with a Send op, which 1) causes an interrupt and 2) includes the info we need to call ib_dma_sync_sg_for_cpu() for the target of the rdma write. We want to omit the Send. If we don't do the sync on the machine that is the target of the RDMA write, the result is... what exactly? I assume the write to memory is snooped by CPUs, so their cachelines will be properly invalidated. However, Linux DMA-API docs seem pretty clear in insisting on the sync. Is the issue IOMMUs? Or for compatibility with bounce buffering? Thanks in advance -- Regards -- Andy -- 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