On 13/06/16 11:58, Shawn Lin wrote: > 在 2016/6/13 16:17, Adrian Hunter 写道: >> On 13/06/16 10:48, Shawn Lin wrote: >>> On 2016/6/13 14:29, Adrian Hunter wrote: >>>> On 06/06/16 06:07, Shawn Lin wrote: >>>>> JEDEC eMMC v5.1 introduce an autonomously initiated method >>>>> for background operations. >>>>> >>>>> Host that wants to enable the device to perform background >>>>> operations during device idle time, should signal the device >>>>> by setting AUTO_EN in BKOPS_EN field EXT_CSD[163] to 1b. When >>>>> this bit is set, the device may start or stop background operations >>>>> whenever it sees fit, without any notification to the host. >>>>> >>>>> When AUTO_EN bit is set, the host should keep the device power >>>>> active. The host may set or clear this bit at any time based on >>>>> its power constraints or other considerations. >>>>> >>>>> Currently the manual bkops is only be used under the async req >>>>> circumstances and it's a bit complicated to be controlled as the >>>>> perfect method is that we should do some idle monitor just as rpm >>>>> and send HPI each time if receiving rd/wr req. But it will impact >>>>> performance significantly, especially for random iops since the >>>>> weight of executing HPI against r/w small piece of LBAs is >>>>> nonnegligible. >>>>> >>>>> So we now prefer to select the auto one unconditionally if supported >>>>> which makes it as simple as possible. It should really good enough >>>>> for devices to manage its internal policy for bkops rather than the >>>>> host, which makes us believe that we could achieve the best >>>>> performance for all the devices implementing auto bkops and the only >>>>> thing we should do is to disable it when cutting off the power. >>>> >>>> Do you know if there is really a requirement to do that? >>> >>> Even without bkops enable, no matter for manual or auto one, FTL should >>> always do bkops like GC internally when needed to guarantee the >>> performance and balance the wear leveling. What I thought to do is to >>> make it more explicitly. >>> >>> Because then, what >>>> is the point of power off notification? >>> >>> When power off notification is sent, bkops will be stopped >>> in _mmc_suspend. So I don't undertand your point here? >> >> I am trying to understand why we need to do anything for auto bkops. >> Since AUTO_EN is persistent, we can leave the decision whether to turn it on >> to whomever provisions the device. Then we just leave it alone. >> > > Hrm.. > > one possible way is to control it by mmc-utils on > user space? So we should add a cmd for mmc-utils > there? That would be consistent with manual bkops. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
