On 15.01.2024 11:46, Viacheslav Dubeyko wrote:
Hi Javier, Samsung introduced Flexible Data Placement (FDP) technology pretty recently. As far as I know, currently, this technology is available for user-space solutions only. I assume it will be good to have discussion how kernel-space file systems could work with SSDs that support FDP technology by employing FDP benefits.
Slava, Thanks for bringing this up. First, this is not a Samsung technology. Several vendors are building FDP and several customers are already deploying first product. We enabled FDP thtough I/O Passthru to avoid unnecesary noise in the block layer until we had a clear idea on use-cases. We have been following and reviewing Bart's write hint series and it covers all the block layer and interface needed to support FDP. Currently, we have patches with small changes to wire the NVMe driver. We plan to submit them after Bart's patches are applied. Now it is a good time since we have LSF and there are also 2 customers using FDP on block and file.
How soon FDP API will be available for kernel-space file systems?
The work is done. We will submit as Bart's patches are applied. Kanchan is doing this work.
How kernel-space file systems can adopt FDP technology?
It is based on write hints. There is no FS-specific placement decisions. All the responsibility is in the application. Kanchan: Can you comment a bit more on this?
How FDP technology can improve efficiency and reliability of kernel-space file system?
This is an open problem. Our experience is that making data placement decisions on the FS is tricky (beyond the obvious data / medatadata). If someone has a good use-case for this, I think it is worth exploring. F2FS is a good candidate, but I am not sure FDP is of interest for mobile - here ZUFS seems to be the current dominant technology.
Which new challenges FDP technology introduces for kernel-space file systems?
See above. All we have done is wire up the NVMe driver. This is a good discussion for LSF/
Could we have such discussion leading from Samsung side?
Of course. We are happy to host a session on this if it gets selected. We will add it to one of our submission.
