On 23 April 2012 21:47, Nick Piggin <npiggin@xxxxxxxxx> wrote: > On 23 April 2012 18:23, James Bottomley >> Experience has taught me to be wary of fine grained hints: they tend to >> be more trouble than they're worth (the definitions are either >> inaccurate or so tediously precise that no-one can be bothered to read >> them). A small set of broad hints is usually more useable than a huge >> set of fine grained ones, so from that point of view, I like the >> O_HOT/O_COLD ones. > > So long as the implementations can be sufficiently general that large majority > of "reasonable" application of the flags does not result in a slowdown, perhaps. > > But while defining the API, you have to think about these things and not > just dismiss them completely. > > Read vs write can be very important for caches and tiers, same for > random/linear, > latency constraints, etc. These things aren't exactly a huge unwieldy matrix. We > already have similar concepts in fadvise and such. I'm not saying it's necessarily a bad idea as such. But experience has taught me that if you define an API before having much experience of the implementation and its users, and without being able to write meaningful documentation for it, then it's going to be a bad API. So rather than pushing through these flags first, I think it would be better to actually do implementation work, and get some benchmarks (if not real apps) and have something working like that before turning anything into an API. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
