add buffer to FEMU Blackbox

[AkmalArifin]

I implemented buffer mechanism in FEMU Blackbox, I also add interface configuration for setting its buffer size and buffer threshold

[wangyuyue]

Thank you for this PR. I notice that the LRU cache is currently only triggered by flash writes. Would adding missed read requests to the flash cache also enhance performance? If so, could you consider using dirty labels to differentiate between clean pages and those requiring write-back during eviction?

[AkmalArifin]

Sorry for the late response. After I adding missed read request to the flash cache, it actually increase the hit ratio constantly after several time of reading.

And for the using dirty labels, I'm sorry could you please elaborate more? Do i just need to add label for the pages that needs to be evicted.

[huaicheng]

Thanks for this, and apologies for the long silence.

A write buffer is genuinely missing — master has a read cache (read_cache_mb) but nothing on the write side, so this is not duplicated by anything that has landed since.

It does not apply as-is: the base here is from 2023 and bbssd has since been split up (ftl-datapath.c, ftl-line-gc.c, ftl-map.c, ftl-cache.c), so it conflicts in a few places. If you are still interested, a rebase onto current master would be very welcome and I will review it promptly — the read cache in ftl-cache.c is a reasonable model for where the hooks now go.

Happy to take it on ourselves instead if you would rather not; just say so and you will still be credited as the author.