Re: SSD "trim" support

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

> Here is a prototype implementation for TRIM (or DELETE or how you
> call it) support for ffs.
> It is inspired by the FreeBSD implementation as this is done
> asynchronously in ffs_blkfree(), before the blocks are actually
> marked free in the filesystem.
> Since ffs (at least NetBSD's) frees blocks in reverse order
> I thought it was a good idea to collapse adjacent blocks
> already at the ffs level where this a-priori knowledge is
> present. This is different from FreeBSD; whether this is worth
> the effort is subject to research.
> This implementation handled only a single block range
> per transaction. SSDs can handle at least 64 vectors with
> one command. Extending the code should be simple.
> 
> I've given this some testing on an Intel and a Kingston
> SSD. Anyone interested in reviewing this, or more tests
> and optimizations?
> (The md(4) backend is for testing only, nothing serious.)

thanks for working on this.

what's the expected behaviour when you read DIOCTRIM'ed blocks?

YAMAMOTO Takashi

> 
> best regards
> Matthias
> 
> 
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