Messages in this thread | | | From | Muchun Song <> | Date | Thu, 29 Oct 2020 21:41:46 +0800 | Subject | Re: [External] Re: [PATCH v2 04/19] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate |
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On Thu, Oct 29, 2020 at 9:26 PM Oscar Salvador <osalvador@suse.de> wrote: > > On Mon, Oct 26, 2020 at 10:50:59PM +0800, Muchun Song wrote: > > If the size of hugetlb page is 2MB, we need 512 struct page structures > > (8 pages) to be associated with it. As far as I know, we only use the > > first 4 struct page structures. > > As Mike pointed out, better describe what those "4" mean.
Yeah, thanks.
> > > For tail pages, the value of compound_dtor is the same. So we can reuse > > I might be missing something, but HUGETLB_PAGE_DTOR is only set on the > first tail, right?
Sorry for confusion. Here I mean the `compound_head` is the same.
> > > +#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP > > +#define RESERVE_VMEMMAP_NR 2U > > Although you can get that from the changelog, maybe a brief comment explaining > why RESERVE_VMEMMAP_NR == 2. > > + > > +static inline unsigned int nr_free_vmemmap(struct hstate *h) > > +{ > > + return h->nr_free_vmemmap_pages; > > +} > > Better add this in the patch that is used?
OK, I will do it. thanks.
> > > + if (vmemmap_pages > RESERVE_VMEMMAP_NR) > > + h->nr_free_vmemmap_pages = vmemmap_pages - RESERVE_VMEMMAP_NR; > > + else > > + h->nr_free_vmemmap_pages = 0; > > Can we really have an scenario where we end up with vmemmap_pages < RESERVE_VMEMMAP_NR?
I think that this is impossible. On the safe side, I do this comparison. Do you think we should remove this comparison? Is that right?
> > > + > > + pr_info("HugeTLB: can free %d vmemmap pages for %s\n", > > + h->nr_free_vmemmap_pages, h->name); > > I do not think this is useful unless debugging situations, so I would either > scratch that or make it pr_debug.
Thanks for your suggestions.
> > > -- > Oscar Salvador > SUSE L3
-- Yours, Muchun
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