On Wed, Feb 16, 2022 at 02:26:18PM -0800, Roman Gushchin wrote: > On Wed, Feb 16, 2022 at 09:55:29PM +0000, Matthew Wilcox wrote: > > On Wed, Feb 16, 2022 at 01:44:10PM -0800, Roman Gushchin wrote: > > > On Wed, Feb 16, 2022 at 09:12:01PM +0000, Matthew Wilcox wrote: > > > > On Wed, Feb 16, 2022 at 12:52:36PM -0800, Roman Gushchin wrote: > > > > > The problem can be fixed by explicitly casting struct page * to struct > > > > > slab * for slab pages. The tools works as expected with this fix, e.g.: > > > > > > > > This feels like a quick fix, and not really correct. > > > > > > Do you mind to provide a correct version? > > > > I know nothing about python, nor how to even run this script. But this > > is the kind of thing I was thinking about. > > > > I didn't do the 'skip over tail pages' because I have no idea how > > you'd tell for_each_page() to do that. I don't know where to get > > drgn.helpers.linux from, so I can't look at the implementation. > > Maybe it already does that. > > Is there an actual plan to set the slab flag for tail pages? > If not, why to check both? It's fairly expensive already, so I'd > not add any additional checks if there is no strict necessity. The plan to set the slab flag on tail pages is probably about five years away. There are a lot of moving parts before we get there. I think you could reduce the cost if we had a for_each_folio() loop. Most code doesn't really want to look at every page, so having a shorter list (and iterating over each page within a folio for the few places that really do want to see every page) would be a good tradeoff. > > @@ -145,14 +145,14 @@ def detect_kernel_config(): > > return cfg > > > > > > -def for_each_slab_page(prog): > > +def for_each_slab(prog): > > Here I'd keep _page (or _folio, if you want), because > it makes it clear that the function goes over all pages > (and is expensive therefore). But there's no intrinsic reason that it should. If that's a performance problem, you could keep slabs on a separate list from, eg, file or anon memory.
