From: James Bottomley <James.Bottomley@HansenPartnership.com> To: Bart Van Assche <firstname.lastname@example.org>, Selva Jove <email@example.com>, firstname.lastname@example.org Cc: email@example.com, firstname.lastname@example.org Subject: Re: [TECH TOPIC] Settling Copy Offload via NVMe SCC Date: Fri, 25 Jun 2021 09:08:29 -0700 [thread overview] Message-ID: <de903dcd41f8881a103a8ca955347b0ef4f176f3.camel@HansenPartnership.com> (raw) In-Reply-To: <email@example.com> On Fri, 2021-06-25 at 09:02 -0700, Bart Van Assche wrote: > On 6/25/21 7:47 AM, Selva Jove wrote: > > The de-facto way of copying data in I/O stack has been pulling it > > from one location followed by pushing to another. The farther the > > application, requiring copy, is from storage, the longer it takes > > for the trip to be over. With copy-offload the trips get shorter as > > the storage device presents an interface to do internal data- > > copying. This enables the host to optimise the pull-and-push > > method, freeing up the host CPU, RAM and the fabric elements. > > > > The copy-offload interface has existed in SCSI storage for at least > > a decade through XCOPY but faced insurmountable challenges in > > getting into the Linux I/O stack. As for NVMe storage, copy-offload > > made its way into the main specification with a new Simple Copy > > Command(SCC) recently. This has stimulated a renewed interest and > > efforts towards copy-offload in the Linux community. > > > > In this talk, we speak of the upstream efforts that we are doing > > around SCC - > > https://firstname.lastname@example.org/#r > > > > We'd extensively cover the design-decisions and seek the feedback > > on the plumbing aspects such as - > > > > 1. User-interface. Should it be a new ioctl/syscall, io_uring based > > opcode or must it fit into existing syscalls such as > > copy_file_range. > > 2. The transport mode between block-layer and NVMe. A chain of > > empty bios (like discard) vs bio with payload. > > 3. Must SCSI XCOPY compatibility be considered while we go about > > building interfaces around NVMe SCC? > > 4. Feasibility and challenges for in-kernel use cases, including > > the file-systems and device-mappers > > This topic seems closely related to "Storage: Copy Offload" > ( > https://lore.kernel.org/linux-block/BYAPR04MB49652C4B75E38F3716F3C06386539@BYAPR04MB4965.namprd04.prod.outlook.com/ > ). Not only that but it would seem to be better suited for LSF/MM on the IO track than the kernel summit track of Plumbers: https://email@example.com/ Since the plumbing aspects are more how would current practitioners use the API and how might we plumb it into filesystems. James > Notes about implementing copy offloading are available at > https://github.com/bvanassche/linux-kernel-copy-offload. > > Thanks, > > Bart. >
next prev parent reply other threads:[~2021-06-25 16:08 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-25 14:47 Selva Jove 2021-06-25 16:02 ` Bart Van Assche 2021-06-25 16:08 ` James Bottomley [this message] 2021-06-29 14:40 ` Selva Jove
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