Messages in this thread | | | Date | Tue, 10 Dec 2019 15:07:58 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] mm: cleanup some useless code |
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On Tue 10-12-19 05:49:10, chengkaitao wrote: > From: Kaitao Cheng <pilgrimtao@gmail.com> > > There is a duplicate PageTransHuge, because hpage_nr_pages have > the same one.
I am not a great fan of changes like these - a minor code churn without a clear benefit - but in this particular case I do agree that there is an improvement because we have two states to represent the same thing. I have hard time believing this makes a more optimal code as PageTransHuge is a trivial check so it doesn't make much sense to replicate the state locally.
That being said the changelog could be improved a bit. What about something like the following? " Compound pages handling in mem_cgroup_migrate is more convoluted than necessary. The state is duplicated in compound variable and the same could be achieved by PageTransHuge check which is trivial and hpage_nr_pages is already PageTransHuge aware.
It is much simpler to just use hpage_nr_pages for nr_pages and replace the local variable by PageTransHuge check directly "
> Signed-off-by: Kaitao Cheng <pilgrimtao@gmail.com>
To the change Acked-by: Michal Hocko <mhocko@suse.com>
Thanks! > --- > mm/memcontrol.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index bc01423277c5..870284d3ee9d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6678,7 +6678,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > { > struct mem_cgroup *memcg; > unsigned int nr_pages; > - bool compound; > unsigned long flags; > > VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); > @@ -6700,8 +6699,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > return; > > /* Force-charge the new page. The old one will be freed soon */ > - compound = PageTransHuge(newpage); > - nr_pages = compound ? hpage_nr_pages(newpage) : 1; > + nr_pages = hpage_nr_pages(newpage); > > page_counter_charge(&memcg->memory, nr_pages); > if (do_memsw_account()) > @@ -6711,7 +6709,8 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > commit_charge(newpage, memcg, false); > > local_irq_save(flags); > - mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages); > + mem_cgroup_charge_statistics(memcg, newpage, PageTransHuge(newpage), > + nr_pages); > memcg_check_events(memcg, newpage); > local_irq_restore(flags); > } > -- > 2.20.1
-- Michal Hocko SUSE Labs
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