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. -- 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
