> On May 14, 2024, at 9:47 PM, Kanchan Joshi <joshiiitr@xxxxxxxxx> wrote: > > On Mon, May 13, 2024 at 2:04 AM Viacheslav Dubeyko <slava@xxxxxxxxxxx> wrote: >> >> >> >>> On May 10, 2024, at 4:40 PM, Kanchan Joshi <joshi.k@xxxxxxxxxxx> wrote: >>> >>> Flexible Data Placement (FDP), as ratified in TP 4146a, allows the host >>> to control the placement of logical blocks so as to reduce the SSD WAF. >>> >>> Userspace can send the data lifetime information using the write hints. >>> The SCSI driver (sd) can already pass this information to the SCSI >>> devices. This patch does the same for NVMe. >>> >>> Fetches the placement-identifiers (plids) if the device supports FDP. >>> And map the incoming write-hints to plids. >>> >> >> >> Great! Thanks for sharing the patch. >> >> Do we have documentation that explains how, for example, kernel-space >> file system can work with block layer to employ FDP? > > This is primarily for user driven/exposed hints. For file system > driven hints, the scheme is really file system specific and therefore, > will vary from one to another. > F2FS is one (and only at the moment) example. Its 'fs-based' policy > can act as a reference for one way to go about it. Yes, I completely see the point. I would like to employ the FDP in my kernel-space file system (SSDFS). And I have a vision how I can do it. But I simply would like to see some documentation with the explanation of API and limitations of FDP for the case of kernel-space file systems. Thanks, Slava.
