From: Oscar Salvador <osalvador@suse.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: akpm@linux-foundation.org, Michal Hocko <mhocko@suse.com>,
Vlastimil Babka <vbabka@suse.cz>,
Logan Gunthorpe <logang@deltatee.com>,
linux-mm@kvack.org, linux-nvdimm@lists.01.org,
linux-kernel@vger.kernel.org, david@redhat.com
Subject: Re: [PATCH v6 03/12] mm/sparsemem: Add helpers track active portions of a section at boot
Date: Fri, 26 Apr 2019 14:57:41 +0200 [thread overview]
Message-ID: <20190426125741.GB28583@linux> (raw)
In-Reply-To: <155552635098.2015392.5460028594173939000.stgit@dwillia2-desk3.amr.corp.intel.com>
On Wed, Apr 17, 2019 at 11:39:11AM -0700, Dan Williams wrote:
> Prepare for hot{plug,remove} of sub-ranges of a section by tracking a
> section active bitmask, each bit representing 2MB (SECTION_SIZE (128M) /
> map_active bitmask length (64)). If it turns out that 2MB is too large
> of an active tracking granularity it is trivial to increase the size of
> the map_active bitmap.
>
> The implications of a partially populated section is that pfn_valid()
> needs to go beyond a valid_section() check and read the sub-section
> active ranges from the bitmask.
>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
[...]
> +static unsigned long section_active_mask(unsigned long pfn,
> + unsigned long nr_pages)
> +{
> + int idx_start, idx_size;
> + phys_addr_t start, size;
> +
> + if (!nr_pages)
> + return 0;
> +
> + start = PFN_PHYS(pfn);
> + size = PFN_PHYS(min(nr_pages, PAGES_PER_SECTION
> + - (pfn & ~PAGE_SECTION_MASK)));
> + size = ALIGN(size, SECTION_ACTIVE_SIZE);
I am probably missing something, and this is more a question than anything else, but:
is there a reason for shifting pfn and pages to get the size and the address?
Could not we operate on pfn/pages, so we do not have to shift every time?
(even for pfn_section_valid() calls)
Something like:
#define SUB_SECTION_ACTIVE_PAGES (SECTION_ACTIVE_SIZE / PAGE_SIZE)
static inline int section_active_index(unsigned long pfn)
{
return (pfn & ~(PAGE_SECTION_MASK)) / SUB_SECTION_ACTIVE_PAGES;
}
> +
> + idx_start = section_active_index(start);
> + idx_size = section_active_index(size);
> +
> + if (idx_size == 0)
> + return -1;
What about turning that into something more intuitive?
Since -1 represents here a full section, we could define something like:
#define FULL_SECTION (-1UL)
Or a better name, it is just that I find "-1" not really easy to interpret.
> + return ((1UL << idx_size) - 1) << idx_start;
> +}
> +
> +void section_active_init(unsigned long pfn, unsigned long nr_pages)
> +{
> + int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
> + int i, start_sec = pfn_to_section_nr(pfn);
> +
> + if (!nr_pages)
> + return;
> +
> + for (i = start_sec; i <= end_sec; i++) {
> + struct mem_section *ms;
> + unsigned long mask;
> + unsigned long pfns;
> +
> + pfns = min(nr_pages, PAGES_PER_SECTION
> + - (pfn & ~PAGE_SECTION_MASK));
> + mask = section_active_mask(pfn, pfns);
> +
> + ms = __nr_to_section(i);
> + pr_debug("%s: sec: %d mask: %#018lx\n", __func__, i, mask);
> + ms->usage->map_active = mask;
> +
> + pfn += pfns;
> + nr_pages -= pfns;
> + }
> +}
> +
> /* Record a memory area against a node. */
> void __init memory_present(int nid, unsigned long start, unsigned long end)
> {
>
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2019-04-26 12:57 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-17 18:38 [PATCH v6 00/12] mm: Sub-section memory hotplug support Dan Williams
2019-04-17 18:39 ` [PATCH v6 01/12] mm/sparsemem: Introduce struct mem_section_usage Dan Williams
2019-05-01 23:25 ` Pavel Tatashin
2019-05-02 6:07 ` Dan Williams
2019-05-02 14:16 ` Pavel Tatashin
2019-05-04 0:22 ` Dan Williams
2019-05-04 15:55 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 02/12] mm/sparsemem: Introduce common definitions for the size and mask of a section Dan Williams
2019-05-02 14:53 ` Pavel Tatashin
2019-05-03 0:41 ` Dan Williams
2019-05-03 10:35 ` Robin Murphy
2019-05-03 12:57 ` Pavel Tatashin
2019-05-03 13:00 ` Oscar Salvador
2019-04-17 18:39 ` [PATCH v6 03/12] mm/sparsemem: Add helpers track active portions of a section at boot Dan Williams
2019-04-25 14:43 ` Oscar Salvador
2019-04-26 12:57 ` Oscar Salvador [this message]
2019-05-02 16:12 ` Pavel Tatashin
2019-05-04 19:26 ` Dan Williams
2019-05-04 19:40 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 04/12] mm/hotplug: Prepare shrink_{zone, pgdat}_span for sub-section removal Dan Williams
2019-04-19 23:09 ` Ralph Campbell
2019-04-19 23:13 ` Dan Williams
2019-04-26 13:59 ` Oscar Salvador
2019-04-26 14:00 ` Oscar Salvador
2019-05-02 19:18 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 05/12] mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap() Dan Williams
2019-05-02 19:28 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 06/12] mm/hotplug: Add mem-hotplug restrictions for remove_memory() Dan Williams
2019-04-23 21:21 ` David Hildenbrand
2019-04-24 18:07 ` Dan Williams
2019-04-17 18:39 ` [PATCH v6 07/12] mm: Kill is_dev_zone() helper Dan Williams
2019-04-17 20:17 ` David Hildenbrand
2019-04-26 14:04 ` Oscar Salvador
2019-05-02 20:37 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 08/12] mm/sparsemem: Prepare for sub-section ranges Dan Williams
2019-05-02 21:25 ` Pavel Tatashin
2019-04-17 18:39 ` [PATCH v6 09/12] mm/sparsemem: Support sub-section hotplug Dan Williams
2019-04-17 18:39 ` [PATCH v6 10/12] mm/devm_memremap_pages: Enable sub-section remap Dan Williams
2019-04-17 18:39 ` [PATCH v6 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields Dan Williams
2019-04-17 22:02 ` Andrew Morton
2019-04-17 22:09 ` Dan Williams
2019-04-17 18:39 ` [PATCH v6 12/12] libnvdimm/pfn: Stop padding pmem namespaces to section alignment Dan Williams
2019-04-17 22:03 ` [PATCH v6 00/12] mm: Sub-section memory hotplug support Andrew Morton
2019-04-17 22:59 ` Dan Williams
2019-04-18 2:09 ` Dan Williams
2019-04-18 12:45 ` Jeff Moyer
2019-04-19 3:25 ` Dan Williams
2019-04-23 13:16 ` Oscar Salvador
2019-04-24 20:43 ` Pavel Tatashin
2019-05-02 22:46 ` Pavel Tatashin
2019-05-02 23:20 ` Dan Williams
2019-05-02 23:21 ` Dan Williams
2019-05-03 10:48 ` Oscar Salvador
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