On Thu 15-02-18 11:59:18, Pavel Tatashin wrote:
> When memory is hotplugged pages_correctly_reserved() is called to verify
> that the added memory is present, this routine traverses through every
> struct page and verifies that PageReserved() is set. This is a slow
> operation especially if a large amount of memory is added.
>
> Instead of checking every page, it is enough to simply check that the
> section is present, has mapping (struct page array is allocated), and the
> mapping is online.
>
> In addition, we should not excpect that probe routine sets flags in struct
> page, as the struct pages have not yet been initialized. The initialization
> should be done in __init_single_page(), the same as during boot.
>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> drivers/base/memory.c | 36 ++++++++++++++++++++----------------
> 1 file changed, 20 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index fe4b24f05f6a..deb3f029b451 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -187,13 +187,14 @@ int memory_isolate_notify(unsigned long val, void *v)
> }
>
> /*
> - * The probe routines leave the pages reserved, just as the bootmem code does.
> - * Make sure they're still that way.
> + * The probe routines leave the pages uninitialized, just as the bootmem code
> + * does. Make sure we do not access them, but instead use only information from
> + * within sections.
> */
> -static bool pages_correctly_reserved(unsigned long start_pfn)
> +static bool pages_correctly_probed(unsigned long start_pfn)
> {
> - int i, j;
> - struct page *page;
> + unsigned long section_nr = pfn_to_section_nr(start_pfn);
> + unsigned long section_nr_end = section_nr + sections_per_block;
> unsigned long pfn = start_pfn;
>
> /*
> @@ -201,21 +202,24 @@ static bool pages_correctly_reserved(unsigned long start_pfn)
> * SPARSEMEM_VMEMMAP. We lookup the page once per section
> * and assume memmap is contiguous within each section
> */
> - for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) {
> + for (; section_nr < section_nr_end; section_nr++) {
> if (WARN_ON_ONCE(!pfn_valid(pfn)))
> return false;
> - page = pfn_to_page(pfn);
> -
> - for (j = 0; j < PAGES_PER_SECTION; j++) {
> - if (PageReserved(page + j))
> - continue;
> -
> - printk(KERN_WARNING "section number %ld page number %d "
> - "not reserved, was it already online?\n",
> - pfn_to_section_nr(pfn), j);
>
> + if (!present_section_nr(section_nr)) {
> + pr_warn("section %ld pfn[%lx, %lx) not present",
> + section_nr, pfn, pfn + PAGES_PER_SECTION);
> + return false;
> + } else if (!valid_section_nr(section_nr)) {
> + pr_warn("section %ld pfn[%lx, %lx) no valid memmap",
> + section_nr, pfn, pfn + PAGES_PER_SECTION);
> + return false;
> + } else if (online_section_nr(section_nr)) {
> + pr_warn("section %ld pfn[%lx, %lx) is already online",
> + section_nr, pfn, pfn + PAGES_PER_SECTION);
> return false;
> }
> + pfn += PAGES_PER_SECTION;
> }
>
> return true;
> @@ -237,7 +241,7 @@ memory_block_action(unsigned long phys_index, unsigned long action, int online_t
>
> switch (action) {
> case MEM_ONLINE:
> - if (!pages_correctly_reserved(start_pfn))
> + if (!pages_correctly_probed(start_pfn))
> return -EBUSY;
>
> ret = online_pages(start_pfn, nr_pages, online_type);
> --
> 2.16.1
>
--
Michal Hocko
SUSE Labs
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