Messages in this thread |  | | Date | Tue, 12 Sep 2000 16:58:06 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | (reiserfs) Re: More on 2.2.18pre2aa2 |
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On Tue, 12 Sep 2000, Rik van Riel wrote:
>But you don't. Transfer rate is very much dependant on the >kind of load you're putting on the disk...
Transfer rate means `hdparm -t` in single user mode. Try it and you'll see you'll get always the same result.
>Throughput really isn't that relevant here. The problems are
Thoughput is relevant. Again, how do you get a 1msec latency out of a blockdevice that writes 1 request every two seconds?
>With equally horrible results for most machines I've >seen. For a while I actually thought the bug /must/ >have been somewhere else because I saw processes >'hanging' for about 10 minutes before making progress >again ...
As said in my earlier email the current 2.4.x elevator scheduler is _disabled_. I repeat: you should change include/linux/elevator.h and set the read and write latency to 250 and 500 respectively. You won't get latency as good as in test1, but it won't hang for 10 minutes.
I and Jens sent a patch to Linus to reenable that push fixing some other problem of the blkdev merging reported by Giuliano Pochini, plus wake-one flow control, plus I fixed the DMA_CHUNK_SIZE thing that was buggy and it's still buggy in the sparc64 case (I didn't fixed sparc64 in my patch, the DMA_CHUNK_SIZE should limit the segments to max(64,SHpnt->sg_tablesize) and not to 64 as now), plus it allowed 512K sized SCSI commands, plus some other minor thing but it didn't get merged.
>Not really. What about just using something like >"half a second, but at least 10 requests liberty to >reorder" ?
I doesn't make sense.
Andrea
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