On 12/5/22 1:29?PM, Michael S. Tsirkin wrote: > On Mon, Dec 05, 2022 at 11:53:51AM -0700, Jens Axboe wrote: >> On 12/5/22 11:36?AM, Alvaro Karsz wrote: >>> Hi, >>> >>>> Is this based on some spec? Because it looks pretty odd to me. There >>>> can be a pretty wide range of two/three/etc level cells with wildly >>>> different ranges of durability. And there's really not a lot of slc >>>> for generic devices these days, if any. >>> >>> Yes, this is based on the virtio spec >>> https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html >>> section 5.2.6 >> >> And where did this come from? > > > Here's the commit log from the spec: > In many embedded systems, virtio-blk implementations are > backed by eMMC or UFS storage devices, which are subject to > predictable and measurable wear over time due to repeated write > cycles. > > For such systems, it can be important to be able to track > accurately the amount of wear imposed on the storage over > time and surface it to applications. In a native deployments > this is generally handled by the physical block device driver > but no such provision is made in virtio-blk to expose these > metrics for devices where it makes sense to do so. > > This patch adds support to virtio-blk for lifetime and wear > metrics to be exposed to the guest when a deployment of > virtio-blk is done over compatible eMMC or UFS storage. > > Signed-off-by: Enrico Granata <egranata@xxxxxxxxxx> > > Cc Enrico Granata as well. Alvaro sent me this one privately too. To be honest, I don't like this patch very much, but that's mostly because the spec for this caters to a narrow use case of embedded flash. It's not a generic storage thing, it's just for mmc/ufs and the embedded space. That's a missed opportunity. And either it'll become mostly unused, or it'll actually be used and then extended at some point. While I'm not a fan at all, if you guys are willing to take it in virtio-blk, then I won't stand in your way. I would rename it though to more specifically detail what it deals with. -- Jens Axboe
