On Thu, Jun 30, 2022 at 04:29:05PM +0900, Dominique MARTINET wrote: > Hi Willy, linux-btrfs@vger, > > Matthew Wilcox (Oracle) wrote on Sun, Jun 19, 2022 at 04:11:41PM +0100: > > We had an off-by-one error which meant that we never marked the first page > > in a read as accessed. This was visible as a slowdown when re-reading > > a file as pages were being evicted from cache too soon. In reviewing > > this code, we noticed a second bug where a multi-page folio would be > > marked as accessed multiple times when doing reads that were less than > > the size of the folio. > > when debugging an unrelated issue (short reads on btrfs with io_uring > and O_DIRECT[1]), I noticed that my horrible big file copy speeds fell > down from ~2GB/s (there's compression and lots of zeroes) to ~100MB/s > the second time I was copying it with cp. > > I've taken a moment to bisect this and came down to this patch. I think you may have forgotten to include the commit-id that was the results of your bisect.... ? - Ted
