From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Disseldorp Subject: Re: [RFC] extending splice for copy offloading Date: Thu, 26 Sep 2013 21:34:51 +0200 Message-ID: <20130926213451.33570dc4@linux-y6zt.site> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-fsdevel , "linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , samba-technical To: Steve French Return-path: In-Reply-To: Sender: linux-cifs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org Hi Steve, On Thu, 26 Sep 2013 12:22:49 -0500 Steve French wrote: > Windows clients seem to max out at 16MB chunk size when doing copy > offload. I would like to increase chunk size larger than that if > network bandwidth (returned at mount time in SMB3 on the query network > interfaces FSCTL) is large enough, and response time is not more than > 100 (?) milliseconds. Sounds good, though with Samba and Btrfs the request latency will be heavily effected by whether the FSCTL_SRV_COPYCHUNK wire request byte offsets and lengths align to the Btrfs sector-size (4K by default IIRC). If they do align, then each chunk in the request can be mapped to a BTRFS_IOC_CLONE_RANGE ioctl. Otherwise, we need to fall back to a server-side local read/write. We should be able to provide underlying filesystem alignment requirements to SMB clients via the new FileFSSectorSizeInformation ioctl, but it's not currently supported by Samba. Cheers, David