LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Pavel Tatashin <pasha.tatashin@oracle.com>
To: David Hildenbrand <david@redhat.com>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Philippe Ombredanne" <pombredanne@nexb.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Michal Hocko" <mhocko@suse.com>, "Jan Kara" <jack@suse.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Matthew Wilcox" <mawilcox@microsoft.com>,
	"Souptick Joarder" <jrdr.linux@gmail.com>,
	"Hugh Dickins" <hughd@google.com>,
	"Huang Ying" <ying.huang@intel.com>,
	"Miles Chen" <miles.chen@mediatek.com>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Reza Arbab" <arbab@linux.vnet.ibm.com>,
	"Mel Gorman" <mgorman@suse.de>,
	"Tetsuo Handa" <penguin-kernel@I-love.SAKURA.ne.jp>
Subject: Re: [PATCH RCFv2 1/7] mm: introduce and use PageOffline()
Date: Mon, 30 Apr 2018 10:35:57 -0400	[thread overview]
Message-ID: <4d112f60-3c24-585e-152e-b42d68c899a2@oracle.com> (raw)
In-Reply-To: <20180430094236.29056-2-david@redhat.com>

Hi Dave,

A few comments below:

> +	for (i = 0; i < PAGES_PER_SECTION; i++) {

Performance wise, this is unfortunate that we have to add this loop for every hot-plug. But, I do like the finer hot-plug granularity that you achieve, and do not have a better suggestion how to avoid this loop. What I also like, is that you call init_single_page() only one time.

> +		unsigned long pfn = phys_start_pfn + i;
> +		struct page *page;
> +		if (!pfn_valid(pfn))
> +			continue;
> +		page = pfn_to_page(pfn);
> +
> +		/* dummy zone, the actual one will be set when onlining pages */
> +		init_single_page(page, pfn, ZONE_NORMAL, nid);

Is there a reason to use ZONE_NORMAL as a dummy zone? May be define some non-existent zone-id for that? I.e. __MAX_NR_ZONES? That might trigger some debugging checks of course..

In init_single_page() if WANT_PAGE_VIRTUAL is defined it is used to set virtual address.  Which is broken if we do not belong to ZONE_NORMAL.

1186	if (!is_highmem_idx(zone))
1187		set_page_address(page, __va(pfn << PAGE_SHIFT));

Otherwise, if you want to keep ZONE_NORMAL here, you could add a new function:

#ifdef WANT_PAGE_VIRTUAL
static void set_page_virtual(struct page *page, and enum zone_type zone)
{
	/* The shift won't overflow because ZONE_NORMAL is below 4G. */
	if (!is_highmem_idx(zone))
		set_page_address(page, __va(pfn << PAGE_SHIFT));
}
#else
static inline void set_page_virtual(struct page *page, and enum zone_type zone)
{}
#endif

And call it from init_single_page(), and from __meminit memmap_init_zone() in "context == MEMMAP_HOTPLUG" if case.

>
> -static void __meminit __init_single_page(struct page *page, unsigned long pfn,
> +extern void __meminit init_single_page(struct page *page, unsigned long pfn,

I've seen it in other places, but what is the point of having "extern" function in .c file?


>  #ifdef CONFIG_MEMORY_HOTREMOVE
> -/* Mark all memory sections within the pfn range as online */
> +static bool all_pages_in_section_offline(unsigned long section_nr)
> +{
> +	unsigned long pfn = section_nr_to_pfn(section_nr);
> +	struct page *page;
> +	int i;
> +
> +	for (i = 0; i < PAGES_PER_SECTION; i++, pfn++) {
> +		if (!pfn_valid(pfn))
> +			continue;
> +
> +		page = pfn_to_page(pfn);
> +		if (!PageOffline(page))
> +			return false;
> +	}
> +	return true;
> +}

Perhaps we could use some counter to keep track of number of subsections that are currently offlined? If section covers 128M of memory, and offline/online is 4M granularity, there are up-to 32 subsections in a section, and thus we need 5-bits to count them. I'm not sure if there is a space in mem_section for this counter. But, that would eliminate the loop above.

Thank you,
Pavel

  reply	other threads:[~2018-04-30 14:35 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-30  9:42 [PATCH RCFv2 0/7] mm: online/offline 4MB chunks controlled by device driver David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 1/7] mm: introduce and use PageOffline() David Hildenbrand
2018-04-30 14:35   ` Pavel Tatashin [this message]
2018-04-30 15:17     ` David Hildenbrand
2018-04-30 15:49       ` David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 2/7] kdump: include PAGE_OFFLINE_MAPCOUNT_VALUE in ELF info David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 3/7] mm/memory_hotplug: limit offline_pages() to sizes we can actually handle David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 4/7] mm/memory_hotplug: allow to control onlining/offlining of memory by a driver David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 5/7] mm/memory_hotplug: print only with DEBUG_VM in offline_pages() David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 6/7] mm/memory_hotplug: teach offline_pages() to not try forever David Hildenbrand
2018-04-30  9:42 ` [PATCH RCFv2 7/7] mm/memory_hotplug: allow online/offline memory by a kernel module David Hildenbrand
2018-05-09 14:14 ` [PATCH RCFv2 0/7] mm: online/offline 4MB chunks controlled by device driver David Hildenbrand

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=4d112f60-3c24-585e-152e-b42d68c899a2@oracle.com \
    --to=pasha.tatashin@oracle.com \
    --cc=akpm@linux-foundation.org \
    --cc=arbab@linux.vnet.ibm.com \
    --cc=dan.j.williams@intel.com \
    --cc=david@redhat.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=hughd@google.com \
    --cc=jack@suse.cz \
    --cc=jglisse@redhat.com \
    --cc=jrdr.linux@gmail.com \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mawilcox@microsoft.com \
    --cc=mgorman@suse.de \
    --cc=mhocko@suse.com \
    --cc=miles.chen@mediatek.com \
    --cc=mingo@kernel.org \
    --cc=penguin-kernel@I-love.SAKURA.ne.jp \
    --cc=pombredanne@nexb.com \
    --cc=tglx@linutronix.de \
    --cc=vbabka@suse.cz \
    --cc=ying.huang@intel.com \
    --subject='Re: [PATCH RCFv2 1/7] mm: introduce and use PageOffline()' \
    /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

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).