Messages in this thread |  | | | Date | Mon, 10 Feb 2003 11:15:39 +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 01:07:25PM +0300, Hans Reiser wrote: > Andrew Morton wrote: > > > > >Large directories tend to be spread all around the disk anyway. And I've > >never explicitly tested for any problems which the loss of readahead might > >have caused ext2. Nor have I tested inode table readahead. Guess I > >should. > > > > > >- > >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > >the body of a message to majordomo@vger.kernel.org > >More majordomo info at http://vger.kernel.org/majordomo-info.html > >Please read the FAQ at http://www.tux.org/lkml/ > > > > > > > > > readahead seems to be less effective for non-sequential objects. Or at
yes, this is why I said readahead matters mostly to generate the big dma commands, so if the object is sequential it will be served by the lowlevel with a single dma using SG. this is also why when I moved the high dma limit of scsi to 512k (from 128k IIRC) I got such a relevant throughput improvement. Also watch the read speed in my tree compared to 2.4 and 2.5 in bigbox.html from Randy (bonnie shows it well).
> least, you don't get the order of magnitude benefit from doing only one > seek, you only get the better elevator scheduling from having more > things in the elevator, which isn't such a big gain.
Agreed.
Andrea - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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