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SubjectRe: [mm PATCH v3 4/6] mm: Move hot-plug specific memory init into separate functions and optimize
On Mon 15-10-18 13:27:16, Alexander Duyck wrote:
> This patch is going through and combining the bits in memmap_init_zone and
> memmap_init_zone_device that are related to hotplug into a single function
> called __memmap_init_hotplug.
>
> I also took the opportunity to integrate __init_single_page's functionality
> into this function. In doing so I can get rid of some of the redundancy
> such as the LRU pointers versus the pgmap.

This patch depends on [1] which I've had some concerns about. It adds
more code on top. I am still not convinced this is the right direction.

[1] http://lkml.kernel.org/r/20180925202053.3576.66039.stgit@localhost.localdomain
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
> mm/page_alloc.c | 232 ++++++++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 159 insertions(+), 73 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 20e9eb35d75d..92375e7867ba 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1192,6 +1192,94 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn,
> #endif
> }
>
> +static void __meminit __init_pageblock(unsigned long start_pfn,
> + unsigned long nr_pages,
> + unsigned long zone, int nid,
> + struct dev_pagemap *pgmap,
> + bool is_reserved)
> +{
> + unsigned long nr_pgmask = pageblock_nr_pages - 1;
> + struct page *start_page = pfn_to_page(start_pfn);
> + unsigned long pfn = start_pfn + nr_pages - 1;
> +#ifdef WANT_PAGE_VIRTUAL
> + bool is_highmem = is_highmem_idx(zone);
> +#endif
> + struct page *page;
> +
> + /*
> + * Enforce the following requirements:
> + * size > 0
> + * size < pageblock_nr_pages
> + * start_pfn -> pfn does not cross pageblock_nr_pages boundary
> + */
> + VM_BUG_ON(((start_pfn ^ pfn) | (nr_pages - 1)) > nr_pgmask);
> +
> + /*
> + * Work from highest page to lowest, this way we will still be
> + * warm in the cache when we call set_pageblock_migratetype
> + * below.
> + *
> + * The loop is based around the page pointer as the main index
> + * instead of the pfn because pfn is not used inside the loop if
> + * the section number is not in page flags and WANT_PAGE_VIRTUAL
> + * is not defined.
> + */
> + for (page = start_page + nr_pages; page-- != start_page; pfn--) {
> + mm_zero_struct_page(page);
> +
> + /*
> + * We use the start_pfn instead of pfn in the set_page_links
> + * call because of the fact that the pfn number is used to
> + * get the section_nr and this function should not be
> + * spanning more than a single section.
> + */
> + set_page_links(page, zone, nid, start_pfn);
> + init_page_count(page);
> + page_mapcount_reset(page);
> + page_cpupid_reset_last(page);
> +
> + /*
> + * We can use the non-atomic __set_bit operation for setting
> + * the flag as we are still initializing the pages.
> + */
> + if (is_reserved)
> + __SetPageReserved(page);
> +
> + /*
> + * ZONE_DEVICE pages union ->lru with a ->pgmap back
> + * pointer and hmm_data. It is a bug if a ZONE_DEVICE
> + * page is ever freed or placed on a driver-private list.
> + */
> + page->pgmap = pgmap;
> + if (!pgmap)
> + INIT_LIST_HEAD(&page->lru);
> +
> +#ifdef WANT_PAGE_VIRTUAL
> + /* The shift won't overflow because ZONE_NORMAL is below 4G. */
> + if (!is_highmem)
> + set_page_address(page, __va(pfn << PAGE_SHIFT));
> +#endif
> + }
> +
> + /*
> + * Mark the block movable so that blocks are reserved for
> + * movable at startup. This will force kernel allocations
> + * to reserve their blocks rather than leaking throughout
> + * the address space during boot when many long-lived
> + * kernel allocations are made.
> + *
> + * bitmap is created for zone's valid pfn range. but memmap
> + * can be created for invalid pages (for alignment)
> + * check here not to call set_pageblock_migratetype() against
> + * pfn out of zone.
> + *
> + * Please note that MEMMAP_HOTPLUG path doesn't clear memmap
> + * because this is done early in sparse_add_one_section
> + */
> + if (!(start_pfn & nr_pgmask))
> + set_pageblock_migratetype(start_page, MIGRATE_MOVABLE);
> +}
> +
> #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> static void __meminit init_reserved_page(unsigned long pfn)
> {
> @@ -5513,6 +5601,36 @@ void __ref build_all_zonelists(pg_data_t *pgdat)
> return false;
> }
>
> +static void __meminit __memmap_init_hotplug(unsigned long size, int nid,
> + unsigned long zone,
> + unsigned long start_pfn,
> + struct dev_pagemap *pgmap)
> +{
> + unsigned long pfn = start_pfn + size;
> +
> + while (pfn != start_pfn) {
> + unsigned long stride = pfn;
> +
> + pfn = max(ALIGN_DOWN(pfn - 1, pageblock_nr_pages), start_pfn);
> + stride -= pfn;
> +
> + /*
> + * The last argument of __init_pageblock is a boolean
> + * value indicating if the page will be marked as reserved.
> + *
> + * Mark page reserved as it will need to wait for onlining
> + * phase for it to be fully associated with a zone.
> + *
> + * Under certain circumstances ZONE_DEVICE pages may not
> + * need to be marked as reserved, however there is still
> + * code that is depending on this being set for now.
> + */
> + __init_pageblock(pfn, stride, zone, nid, pgmap, true);
> +
> + cond_resched();
> + }
> +}
> +
> /*
> * Initially all pages are reserved - free ones are freed
> * up by memblock_free_all() once the early boot process is
> @@ -5523,51 +5641,61 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> struct vmem_altmap *altmap)
> {
> unsigned long pfn, end_pfn = start_pfn + size;
> - struct page *page;
>
> if (highest_memmap_pfn < end_pfn - 1)
> highest_memmap_pfn = end_pfn - 1;
>
> + if (context == MEMMAP_HOTPLUG) {
> #ifdef CONFIG_ZONE_DEVICE
> - /*
> - * Honor reservation requested by the driver for this ZONE_DEVICE
> - * memory. We limit the total number of pages to initialize to just
> - * those that might contain the memory mapping. We will defer the
> - * ZONE_DEVICE page initialization until after we have released
> - * the hotplug lock.
> - */
> - if (zone == ZONE_DEVICE) {
> - if (!altmap)
> - return;
> + /*
> + * Honor reservation requested by the driver for this
> + * ZONE_DEVICE memory. We limit the total number of pages to
> + * initialize to just those that might contain the memory
> + * mapping. We will defer the ZONE_DEVICE page initialization
> + * until after we have released the hotplug lock.
> + */
> + if (zone == ZONE_DEVICE) {
> + if (!altmap)
> + return;
> +
> + if (start_pfn == altmap->base_pfn)
> + start_pfn += altmap->reserve;
> + end_pfn = altmap->base_pfn +
> + vmem_altmap_offset(altmap);
> + }
> +#endif
> + /*
> + * For these ZONE_DEVICE pages we don't need to record the
> + * pgmap as they should represent only those pages used to
> + * store the memory map. The actual ZONE_DEVICE pages will
> + * be initialized later.
> + */
> + __memmap_init_hotplug(end_pfn - start_pfn, nid, zone,
> + start_pfn, NULL);
>
> - if (start_pfn == altmap->base_pfn)
> - start_pfn += altmap->reserve;
> - end_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
> + return;
> }
> -#endif
>
> for (pfn = start_pfn; pfn < end_pfn; pfn++) {
> + struct page *page;
> +
> /*
> * There can be holes in boot-time mem_map[]s handed to this
> * function. They do not exist on hotplugged memory.
> */
> - if (context == MEMMAP_EARLY) {
> - if (!early_pfn_valid(pfn)) {
> - pfn = next_valid_pfn(pfn) - 1;
> - continue;
> - }
> - if (!early_pfn_in_nid(pfn, nid))
> - continue;
> - if (overlap_memmap_init(zone, &pfn))
> - continue;
> - if (defer_init(nid, pfn, end_pfn))
> - break;
> + if (!early_pfn_valid(pfn)) {
> + pfn = next_valid_pfn(pfn) - 1;
> + continue;
> }
> + if (!early_pfn_in_nid(pfn, nid))
> + continue;
> + if (overlap_memmap_init(zone, &pfn))
> + continue;
> + if (defer_init(nid, pfn, end_pfn))
> + break;
>
> page = pfn_to_page(pfn);
> __init_single_page(page, pfn, zone, nid);
> - if (context == MEMMAP_HOTPLUG)
> - __SetPageReserved(page);
>
> /*
> * Mark the block movable so that blocks are reserved for
> @@ -5594,14 +5722,12 @@ void __ref memmap_init_zone_device(struct zone *zone,
> unsigned long size,
> struct dev_pagemap *pgmap)
> {
> - unsigned long pfn, end_pfn = start_pfn + size;
> struct pglist_data *pgdat = zone->zone_pgdat;
> unsigned long zone_idx = zone_idx(zone);
> unsigned long start = jiffies;
> int nid = pgdat->node_id;
>
> - if (WARN_ON_ONCE(!pgmap || !is_dev_zone(zone)))
> - return;
> + VM_BUG_ON(!is_dev_zone(zone));
>
> /*
> * The call to memmap_init_zone should have already taken care
> @@ -5610,53 +5736,13 @@ void __ref memmap_init_zone_device(struct zone *zone,
> */
> if (pgmap->altmap_valid) {
> struct vmem_altmap *altmap = &pgmap->altmap;
> + unsigned long end_pfn = start_pfn + size;
>
> start_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
> size = end_pfn - start_pfn;
> }
>
> - for (pfn = start_pfn; pfn < end_pfn; pfn++) {
> - struct page *page = pfn_to_page(pfn);
> -
> - __init_single_page(page, pfn, zone_idx, nid);
> -
> - /*
> - * Mark page reserved as it will need to wait for onlining
> - * phase for it to be fully associated with a zone.
> - *
> - * We can use the non-atomic __set_bit operation for setting
> - * the flag as we are still initializing the pages.
> - */
> - __SetPageReserved(page);
> -
> - /*
> - * ZONE_DEVICE pages union ->lru with a ->pgmap back
> - * pointer and hmm_data. It is a bug if a ZONE_DEVICE
> - * page is ever freed or placed on a driver-private list.
> - */
> - page->pgmap = pgmap;
> - page->hmm_data = 0;
> -
> - /*
> - * Mark the block movable so that blocks are reserved for
> - * movable at startup. This will force kernel allocations
> - * to reserve their blocks rather than leaking throughout
> - * the address space during boot when many long-lived
> - * kernel allocations are made.
> - *
> - * bitmap is created for zone's valid pfn range. but memmap
> - * can be created for invalid pages (for alignment)
> - * check here not to call set_pageblock_migratetype() against
> - * pfn out of zone.
> - *
> - * Please note that MEMMAP_HOTPLUG path doesn't clear memmap
> - * because this is done early in sparse_add_one_section
> - */
> - if (!(pfn & (pageblock_nr_pages - 1))) {
> - set_pageblock_migratetype(page, MIGRATE_MOVABLE);
> - cond_resched();
> - }
> - }
> + __memmap_init_hotplug(size, nid, zone_idx, start_pfn, pgmap);
>
> pr_info("%s initialised, %lu pages in %ums\n", dev_name(pgmap->dev),
> size, jiffies_to_msecs(jiffies - start));
>

--
Michal Hocko
SUSE Labs

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