On Mon, Jun 28, 2021 at 03:28:19AM +0000, Justin He wrote: > > On which loads? 1 here is "mount/dentry pair is in somebody > > else's namespace or outside of the subtree we are chrooted > > into". IOW, what's calling d_path() on your setup? > > No special loads, merely collecting the results after kernel boots up. > > To narrow down, I tested your branch [1] *without* my '%pD' series: > [1] https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/log/?h=work.d_path > > The result is the same after kernel boots up. IOW, you get 1 in call from d_absolute_path(). And the same commit has - if (prepend_path(path, &root, &b) > 1) + if (unlikely(prepend_path(path, &root, &b) > 1)) there. What's the problem? If you want to check mispredictions, put printks at the statements under those if (unlikely(...)) and see how often do they trigger...
