On Sat, 2013-09-14 at 23:33 +0200, Thiemo Nagel wrote: [...] > What I take away from this: For optimal performance, the frequency of > syncs should be kept low, probably well below 50 Hz, ideally as low as > possible. I'd be in favour of removing them altogether, but there > were some OOM issues seven years ago that were fixed by adding them. > Does anybody know whether bug 381135 still applies with today's > kernels? I believe Linux will throttle writing processes so that the size of buffered writes doesn't keep growing. And I have never seen problems when wiping disks with dd (I disposed of a whole bunch of old disks recently) without periodic sync'ing. However, the size of buffered writes can still grow quite large, which will limit the accuracy of a progress display. So I would suggest you sync whenever you're about to indicate progress, but also increase the granularity of progress (65536 steps is ridiculous) so that doesn't happen too often. > In any case, I'd suggest to go at least for 1M block size, even if > just to reduce the amount of system calls. [...] It looks like 1 MB is just about enough to maximise throughput, and this matches my memory. Ben. -- Ben Hutchings If at first you don't succeed, you're doing about average.
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