Posted Feb 7, 2010 3:36 UTC (Sun) by giraffedata
In reply to: Improving readahead
Parent article: Improving readahead
Note that this effect isn't present if the application doesn't have
any processing to do.
Nope. Two reasons:
...there will always be some latency between
the end of one request and the beginning of the next
OK, I did oversimplify when I referred to an application with no processing to do, as that's impossible. To be more precise, I could say to the extent that an application has no processing to do, this overlap effect of readahead doesn't produce any application speedup. There will always be some speedup.
When *other* applications have the CPU, the disk could go idle too.
Readahead could be still issuing requests on behalf of the app during
I guess you're talking about time the application is waiting for the CPU, which the readahead overlaps as well. Yes, I missed that. But in an I/O-bound application, this should be negligible, shouldn't it? With decent CPU allocation/scheduling, the process ought to get scheduled really soon after its read completes and keep the CPU until it starts the next one.
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