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Joel Becker wrote: >>I think what happened was that the number of iocbs submitted (64 iocbs >>of 4K each) did not merge because the device queue depth was very large; >>no queuing occured because (I imagine) merging happens while a request >>is waiting for disk readiness. >> >> > > Why did you submit 64 iocbs of 4K? Was every page virtually >discontiguous, or did you arbitrarily decide to create a worst-case? > > The application (a userspace filesystem with its own cache) manages memory in 4K pages, but can perform much larger I/Os, for example during readahead and after merging writes. After a very short while memory is completely fragmented. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. - 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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