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On 12-Feb-2004 Andrea Arcangeli wrote: > the main difference is that 2.4 isn't in function of time, it's in > function of requests, no matter how long it takes to write a request, > so it's potentially optimizing slow devices when you don't care about > latency (deadline can be tuned for each dev via> /sys/block/*/queue/iosched/). IMHO it's the opposite. Transfer speed * seek time of some slow devices is lower than fast devices. For example: Hard disk raw speed= 40MB/s seek time = 8ms MO/ZIP raw speed= 3MB/s seek time = 25ms One seek of HD costs about 320KB, while on a slow drive it's only 75KB. 2.4 has a terrible latency on slow devices, and it has very small advantage in terms of speed. On CDs and DVDs the cost of a seek is much higher, but since the data is usually accessed sequentially you have the high latency penalty with no appreciable speed gain in this case too. -- Giuliano. - 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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