On Tue, May 16, 2023 at 01:26:08AM +0800, Yuanchu Xie wrote: > The pagewalk in pagemap_read reads one PTE past the end of the requested > range, and stops when the buffer runs out of space. While it produces > the right result, the extra read is unnecessary and less performant. > > I timed the following command before and after this patch: > dd count=100000 if=/proc/self/pagemap of=/dev/null > The results are consistently within 0.001s across 5 runs. > > Before: > 100000+0 records in > 100000+0 records out > 51200000 bytes (51 MB) copied, 0.0763159 s, 671 MB/s > > real 0m0.078s > user 0m0.012s > sys 0m0.065s > > After: > 100000+0 records in > 100000+0 records out > 51200000 bytes (51 MB) copied, 0.0487928 s, 1.0 GB/s > > real 0m0.050s > user 0m0.011s > sys 0m0.039s > > Signed-off-by: Yuanchu Xie <yuanchu@xxxxxxxxxx> Acked-by: Peter Xu <peterx@xxxxxxxxxx> -- Peter Xu
