Messages in this thread |  | | From | Nikita Danilov <> | Date | Fri, 24 Jan 2003 15:14:40 +0300 | Subject | Re: 2.5.59-mm5 |
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Andrew Morton writes:
[...]
> > In this very common scenario, the only way we'll ever get "lumps" of reads is > if some other processes come in and happen to want to read nearby sectors.
Or if you have read-ahead for meta-data, which is quite useful. Isn't read ahead targeting the same problem as this anticipatory scheduling?
> In the best case, the size of the lump is proportional to the number of > processes which are concurrently trying to read something. This just doesn't > happen enough to be significant or interesting. > > But writes are completely different. There is no dependency between them and > at any point in time we know where on-disk a lot of writes will be placed. > We don't know that for reads, which is why we need to twiddle thumbs until the > application or filesystem makes up its mind. >
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