From: Baoquan He <bhe@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>,
David Hildenbrand <david@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Wei Yang <richardw.yang@linux.intel.com>
Subject: Re: [PATCH 3/7] mm/sparse.c: only use subsection map in VMEMMAP case
Date: Wed, 12 Feb 2020 19:20:00 +0800 [thread overview]
Message-ID: <20200212112000.GH8965@MiWiFi-R3L-srv> (raw)
In-Reply-To: <B23A05D9-40E2-4862-979D-C6DA69DDDC80@redhat.com>
On 02/12/20 at 10:39am, David Hildenbrand wrote:
>
>
> > Am 11.02.2020 um 21:15 schrieb Dan Williams <dan.j.williams@intel.com>:
> >
> > On Sun, Feb 9, 2020 at 2:48 AM Baoquan He <bhe@redhat.com> wrote:
> >>
> >> Currently, subsection map is used when SPARSEMEM is enabled, including
> >> VMEMMAP case and !VMEMMAP case. However, subsection hotplug is not
> >> supported at all in SPARSEMEM|!VMEMMAP case, subsection map is unnecessary
> >> and misleading. Let's adjust code to only allow subsection map being
> >> used in SPARSEMEM|VMEMMAP case.
> >>
> >> Signed-off-by: Baoquan He <bhe@redhat.com>
> >> ---
> >> include/linux/mmzone.h | 2 +
> >> mm/sparse.c | 231 ++++++++++++++++++++++-------------------
> >> 2 files changed, 124 insertions(+), 109 deletions(-)
> >>
> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> >> index 462f6873905a..fc0de3a9a51e 100644
> >> --- a/include/linux/mmzone.h
> >> +++ b/include/linux/mmzone.h
> >> @@ -1185,7 +1185,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
> >> #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
> >>
> >> struct mem_section_usage {
> >> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> >> DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
> >> +#endif
> >
> > This was done deliberately so that the SPARSEMEM_VMEMMAP=n case ran as
> > a subset of the SPARSEMEM_VMEMMAP=y case.
Thanks for checking this, Dan.
Taking away the subsection part, won't affect the classic sparse being a
subset of VMEMMAP case, I would say.
> >
> > The diffstat does not seem to agree that this is any clearer:
> >
> > 124 insertions(+), 109 deletions(-)
> >
>
> I don‘t see a reason to work with subsections (+store them) if subsections are not supported.
>
> I do welcome this cleanup. Diffstats don‘t tell the whole story.
Thanks for clarifying this, David, I agree.
If applying the patch, it should be easier to observe that the code
is simpler to follow, at least won't be confusing on subsection handling
part.
next prev parent reply other threads:[~2020-02-12 11:20 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-09 10:48 [PATCH 0/7] mm/hotplug: Only use subsection in VMEMMAP case and fix hot add/remove failure in SPARSEMEM|!VMEMMAP case Baoquan He
2020-02-09 10:48 ` [PATCH 1/7] mm/sparse.c: Introduce new function fill_subsection_map() Baoquan He
2020-02-09 23:05 ` Wei Yang
2020-02-09 23:11 ` Wei Yang
2020-02-10 3:25 ` Baoquan He
2020-02-10 9:49 ` David Hildenbrand
2020-02-11 12:46 ` Baoquan He
2020-02-11 14:44 ` David Hildenbrand
2020-02-12 11:21 ` Baoquan He
2020-02-09 10:48 ` [PATCH 2/7] mm/sparse.c: Introduce a new function clear_subsection_map() Baoquan He
2020-02-09 23:07 ` Wei Yang
2020-02-10 3:36 ` Baoquan He
2020-02-10 6:02 ` Wei Yang
2020-02-09 10:48 ` [PATCH 3/7] mm/sparse.c: only use subsection map in VMEMMAP case Baoquan He
2020-02-09 23:23 ` Wei Yang
2020-02-11 14:43 ` David Hildenbrand
2020-02-12 11:26 ` Baoquan He
2020-02-11 20:14 ` Dan Williams
2020-02-12 9:39 ` David Hildenbrand
2020-02-12 11:20 ` Baoquan He [this message]
2020-02-12 15:48 ` Dan Williams
2020-02-09 10:48 ` [PATCH 4/7] mm/sparse.c: Use __get_free_pages() instead in populate_section_memmap() Baoquan He
2020-02-09 23:39 ` Wei Yang
2020-02-09 10:48 ` [PATCH 5/7] mm/sparse.c: update code comment about section activate/deactivate Baoquan He
2020-02-09 10:48 ` [PATCH 6/7] mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM Baoquan He
2020-02-10 3:45 ` Baoquan He
2020-02-09 10:48 ` [PATCH 7/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case Baoquan He
2020-02-09 23:52 ` Wei Yang
2020-02-10 3:41 ` Baoquan He
2020-02-10 6:08 ` Wei Yang
2020-02-10 7:54 ` Baoquan He
2020-02-10 23:05 ` Wei Yang
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=20200212112000.GH8965@MiWiFi-R3L-srv \
--to=bhe@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dan.j.williams@intel.com \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=richardw.yang@linux.intel.com \
/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).