On Sun, 2017-04-09 at 11:15 +0200, Javier González wrote: > On 8 Apr 2017, at 22.56, Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > > On 04/07/17 11:50, Javier González wrote: > struct ppa_addr, which is the physical address format is not affected, > but pblk's internal L2P address representation (pblk_addr) is. You can > see that the type either represents struct ppa_addr or ppa_addr_32. How > would you define a type that can either be u64 or u32 with different bit > offsets at run-time? Note that address conversions to this type is in > the fast path and this format allows us to only use bit shifts. Selecting the appropriate representation at run-time would require to pass pblk_addr by reference instead of by value to any function that expects a pblk_addr. It would also require to have two versions of every data structure that depends on pblk_addr and to use casts to convert to the appropritate version. However, this approach is probably only worth to be implemented if it doesn't introduce too much additional complexity. > > > +#ifdef CONFIG_NVM_DEBUG > > > + atomic_add(nr_entries, &pblk->inflight_writes); > > > + atomic_add(nr_entries, &pblk->req_writes); > > > +#endif > > > > Has it been considered to use the "static key" feature such that > > consistency checks can be enabled at run-time instead of having to > > rebuild the kernel to enable CONFIG_NVM_DEBUG? > > I haven't considered it. I'll look into it. I would like to have this > counters and the corresponding sysfs entry only available on debug mode > since it allows us to have a good picture of the FTL state. If there are sysfs entries that depend on CONFIG_NVM_DEBUG then the static key mechanism is probably not a good alternative for CONFIG_NVM_DEBUG. > > Has it been considered to add support for keeping a subset of the L2P > > translation table in memory instead of keeping it in memory in its entirety? > > Yes. L2P caching is on our roadmap and will be included in the future. That's great. This will also help with reducing the time between discovery of a lightnvm device and the time at which I/O can start since the L2P table must be available before I/O can start. Bart.
