On Mon, May 17, 2021 at 03:21:20PM +0300, Andrei POPESCU wrote: [...]
> If my understanding from your quotes and David's links is correct > oflag=sync may be slower in specific circumstances, but it depends on so > many factors (hardware, caches, block size used, etc.) that it is hard > to predict. The proof would be in the pudding, of course. > Quite likely it won't make a significant difference for "regular" use. For regular use, the oflag is (as I tried to explain) invaluable to me. See, I bought myself a refurbished notebook, but I didn't skimp on RAM: 16GB. My main dd use is to write some image onto a flash removable (stick, SD card). The write channel is slow, the available buffer big. Once the write is done (if I do cp or forget the sync), not much is actually written to the drive. Then I say "sync", and... the sync goes shopping, without telling me when it plans to be back :-) With "oflags=sync status=progress" (or by sending SIGHUP to the dd process) I can get a rough idea when I'll be able to pull out that stick. Needless to say, I don't mind the copy being some, say, 10% slower (totally making that up, but for a seq writing with some biggish block size, I'd expect even that to be an outrageous exaggeration). Cheers - t
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