Messages in this thread | | | Date | Mon, 10 Feb 2003 09:56:49 +0100 | From | Andrea Arcangeli <> | Subject | Re: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest] |
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On Mon, Feb 10, 2003 at 12:19:21AM -0800, Andrew Morton wrote: > Andrea Arcangeli <andrea@suse.de> wrote: > > > > BTW, one thing that should definitely do readhaead and it's > > not doing that (at least in 2.4) is the readdir path, again to generate > > big commands, no matter the seeks. It was lost with the directory in > > pagecache. > > Yes. But ext3 is still doing directory readahead, and I have never > noticed it gaining any particular benefit over ext2 from it.
At least for big directories it should be at least a quite obvious microoptimization, if you do it at the logical level. Maybe it wasn't worthwhile in the past (like in ext3) because it was done at the block layer with a dumb reada rather than with proper read of the next logical block before wait_on_buffer. Also keep in mind the max readahead generated by the block layer is nothing compared to the true readahead that the logical layer is able to generate.
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