Messages in this thread | | | Subject | Re: Linux 5.9-rc7 / VmallocTotal wrongly reported | From | Vlastimil Babka <> | Date | Fri, 2 Oct 2020 10:51:27 +0200 |
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On 10/1/20 10:39 PM, Roman Gushchin wrote: > On Thu, Oct 01, 2020 at 12:58:36PM -0700, Linus Torvalds wrote: >> On Thu, Oct 1, 2020 at 12:56 PM Roman Gushchin <guro@fb.com> wrote: >> > >> > Bastian, can you, please, share your config? >> >> Bastian actually did that in the original email, but that was only >> sent to me and Andrew in private. >> >> Here's that config replicated for your pleasure, > > Thank you! > >> >> # >> # Processor type and features >> # >> # CONFIG_ZONE_DMA is not set >> # CONFIG_SMP is not set > > Yes, here is the deal. > > The SMP-version of __mod_node_page_state() converts a passed value from bytes > to pages, but the non-SMP doesn't. > > Thanks! > > > -- > > From 3d0233b37340c78012b991d3570b92f91cf5ebd2 Mon Sep 17 00:00:00 2001 > From: Roman Gushchin <guro@fb.com> > Date: Thu, 1 Oct 2020 13:07:49 -0700 > Subject: [PATCH] mm: memcg/slab: fix slab statistics in !SMP configuration > > Since ea426c2a7de8 ("mm: memcg: prepare for byte-sized vmstat items") > the write side of slab counters accepts a value in bytes and converts > it to pages. It happens in __mod_node_page_state(). > > However a non-SMP version of __mod_node_page_state() doesn't perform > this conversion. It leads to incorrect (unrealistically high) slab > counters values. Fix this by adding a similar conversion to the > non-SMP version of __mod_node_page_state(). > > Signed-off-by: Roman Gushchin <guro@fb.com> > Reported-by: Bastian Bittorf <bb@npl.de> > Fixes: ea426c2a7de8 ("mm: memcg: prepare for byte-sized vmstat items")
Acked-by: Vlastimil Babka <vbabka@suse.cz>
For consistency we could also duplicate the "VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));" in !SMP variants of __inc_node_state() and __dec_node_state(), but that's not urgent, and perhaps SMP configs are enough to catch any bugs introduced in the future in this area...
> --- > include/linux/vmstat.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > index d5431c1bf6e5..322dcbfcc933 100644 > --- a/include/linux/vmstat.h > +++ b/include/linux/vmstat.h > @@ -312,6 +312,11 @@ static inline void __mod_zone_page_state(struct zone *zone, > static inline void __mod_node_page_state(struct pglist_data *pgdat, > enum node_stat_item item, int delta) > { > + if (vmstat_item_in_bytes(item)) { > + VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1)); > + delta >>= PAGE_SHIFT; > + } > + > node_page_state_add(delta, pgdat, item); > } > >
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