From: Michal Hocko <mhocko@kernel.org>
To: KarimAllah Ahmed <karahmed@amazon.de>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mel Gorman" <mgorman@techsingularity.net>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Yaowei Bai" <baiyaowei@cmss.chinamobile.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Joe Perches" <joe@perches.com>, "Tejun Heo" <tj@kernel.org>,
"Anthony Liguori" <aliguori@amazon.com>,
"Jan H . Schönherr" <jschoenh@amazon.de>
Subject: Re: [PATCH] sparse: Track the boundaries of memory sections for accurate checks
Date: Mon, 20 Jun 2016 10:23:40 +0200 [thread overview]
Message-ID: <20160620082339.GC4340@dhcp22.suse.cz> (raw)
In-Reply-To: <1466244679-23824-1-git-send-email-karahmed@amazon.de>
On Sat 18-06-16 12:11:19, KarimAllah Ahmed wrote:
> When sparse memory model is used an array of memory sections is created to
> track each block of contiguous physical pages. Each element of this array
> contains PAGES_PER_SECTION pages. During the creation of this array the actual
> boundaries of the memory block is lost, so the whole block is either considered
> as present or not.
>
> pfn_valid() in the sparse memory configuration checks which memory sections the
> pfn belongs to then checks whether it's present or not. This yields sub-optimal
> results when the available memory doesn't cover the whole memory section,
> because pfn_valid will return 'true' even for the unavailable pfns at the
> boundaries of the memory section.
Please be more verbose of _why_ the patch is needed. Why those
"sub-optimal results" matter?
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Anthony Liguori <aliguori@amazon.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
> Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
> ---
> include/linux/mmzone.h | 22 ++++++++++++++++------
> mm/sparse.c | 37 ++++++++++++++++++++++++++++++++++++-
> 2 files changed, 52 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 02069c2..f76a0e1 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1067,8 +1067,12 @@ struct mem_section {
> * section. (see page_ext.h about this.)
> */
> struct page_ext *page_ext;
> - unsigned long pad;
> + unsigned long pad[3];
> #endif
> +
> + unsigned long first_pfn;
> + unsigned long last_pfn;
> +
> /*
> * WARNING: mem_section must be a power-of-2 in size for the
> * calculation and use of SECTION_ROOT_MASK to make sense.
> @@ -1140,23 +1144,29 @@ static inline int valid_section_nr(unsigned long nr)
>
> static inline struct mem_section *__pfn_to_section(unsigned long pfn)
> {
> + if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> + return NULL;
> +
> return __nr_to_section(pfn_to_section_nr(pfn));
> }
>
> #ifndef CONFIG_HAVE_ARCH_PFN_VALID
> static inline int pfn_valid(unsigned long pfn)
> {
> - if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> + struct mem_section *ms;
> +
> + ms = __pfn_to_section(pfn);
> +
> + if (ms && !(ms->first_pfn <= pfn && ms->last_pfn >= pfn))
> return 0;
> - return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
> +
> + return valid_section(ms);
> }
> #endif
>
> static inline int pfn_present(unsigned long pfn)
> {
> - if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> - return 0;
> - return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
> + return present_section(__pfn_to_section(pfn));
> }
>
> /*
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 5d0cf45..3c91837 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -166,24 +166,59 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
> }
> }
>
> +static int __init
> +overlaps(u64 start1, u64 end1, u64 start2, u64 end2)
> +{
> + u64 start, end;
> +
> + start = max(start1, start2);
> + end = min(end1, end2);
> + return start <= end;
> +}
> +
> /* Record a memory area against a node. */
> void __init memory_present(int nid, unsigned long start, unsigned long end)
> {
> + unsigned long first_pfn = start;
> unsigned long pfn;
>
> start &= PAGE_SECTION_MASK;
> mminit_validate_memmodel_limits(&start, &end);
> for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
> unsigned long section = pfn_to_section_nr(pfn);
> + unsigned long last_pfn = min(pfn + PAGES_PER_SECTION, end) - 1;
> struct mem_section *ms;
>
> sparse_index_init(section, nid);
> set_section_nid(section, nid);
>
> ms = __nr_to_section(section);
> - if (!ms->section_mem_map)
> + if (!ms->section_mem_map) {
> ms->section_mem_map = sparse_encode_early_nid(nid) |
> SECTION_MARKED_PRESENT;
> + } else {
> + /* Merge the two regions */
> + WARN_ON(sparse_early_nid(ms) != nid);
> +
> + /*
> + * If they don't overlap there will be a hole in
> + * between where meta-data says it's valid even though
> + * it's not.
> + */
> + if (!overlaps(first_pfn, last_pfn + 1,
> + ms->first_pfn, ms->last_pfn + 1)) {
> + pr_info("Merging non-contiguous pfn ranges 0x%lx-0x%lx and 0x%lx-0x%lx\n",
> + ms->first_pfn, ms->last_pfn,
> + first_pfn, last_pfn);
> + }
> + first_pfn = min(first_pfn, ms->first_pfn);
> + last_pfn = max(last_pfn, ms->last_pfn);
> + }
> +
> + ms->first_pfn = first_pfn;
> + ms->last_pfn = last_pfn;
> +
> + first_pfn = pfn + PAGES_PER_SECTION;
> }
> }
>
> --
> 2.8.2
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-06-20 8:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-18 10:11 [PATCH] sparse: Track the boundaries of memory sections for accurate checks KarimAllah Ahmed
2016-06-20 8:23 ` Michal Hocko [this message]
2016-06-21 14:33 ` [PATCH v2] " KarimAllah Ahmed
2016-09-14 21:40 ` [PATCH] " Raslan, KarimAllah
2016-09-14 22:05 ` Dan Williams
2016-09-14 22:11 ` Raslan, KarimAllah
2016-09-14 22:53 ` Dan Williams
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160620082339.GC4340@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=aliguori@amazon.com \
--cc=baiyaowei@cmss.chinamobile.com \
--cc=dan.j.williams@intel.com \
--cc=hannes@cmpxchg.org \
--cc=joe@perches.com \
--cc=jschoenh@amazon.de \
--cc=karahmed@amazon.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=tj@kernel.org \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).