From: Ingo Molnar <mingo@kernel.org>
To: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
akpm@linux-foundation.org, mgorman@techsingularity.net,
mhocko@suse.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org,
vbabka@suse.cz, bharata@linux.vnet.ibm.com, tglx@linutronix.de,
mingo@redhat.com, hpa@zytor.com, x86@kernel.org,
dan.j.williams@intel.com, kirill.shutemov@linux.intel.com,
bhe@redhat.com
Subject: Re: [v4 6/6] mm/memory_hotplug: optimize memory hotplug
Date: Fri, 16 Feb 2018 10:30:00 +0100 [thread overview]
Message-ID: <20180216092959.gkm6d4j2zplk724r@gmail.com> (raw)
In-Reply-To: <20180215165920.8570-7-pasha.tatashin@oracle.com>
* Pavel Tatashin <pasha.tatashin@oracle.com> wrote:
> During memory hotplugging we traverse struct pages three times:
>
> 1. memset(0) in sparse_add_one_section()
> 2. loop in __add_section() to set do: set_page_node(page, nid); and
> SetPageReserved(page);
> 3. loop in memmap_init_zone() to call __init_single_pfn()
>
> This patch remove the first two loops, and leaves only loop 3. All struct
> pages are initialized in one place, the same as it is done during boot.
s/remove
/removes
> The benefits:
> - We improve the memory hotplug performance because we are not evicting
> cache several times and also reduce loop branching overheads.
s/We improve the memory hotplug performance
/We improve memory hotplug performance
s/not evicting cache several times
/not evicting the cache several times
s/overheads
/overhead
> - Remove condition from hotpath in __init_single_pfn(), that was added in
> order to fix the problem that was reported by Bharata in the above email
> thread, thus also improve the performance during normal boot.
s/improve the performance
/improve performance
> - Make memory hotplug more similar to boot memory initialization path
> because we zero and initialize struct pages only in one function.
s/more similar to boot memory initialization path
/more similar to the boot memory initialization path
> - Simplifies memory hotplug strut page initialization code, and thus
> enables future improvements, such as multi-threading the initialization
> of struct pages in order to improve the hotplug performance even further
> on larger machines.
s/strut
/struct
s/to improve the hotplug performance even further
/to improve hotplug performance even further
> @@ -260,21 +260,12 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
> return ret;
>
> /*
> - * Make all the pages reserved so that nobody will stumble over half
> - * initialized state.
> - * FIXME: We also have to associate it with a node because page_to_nid
> - * relies on having page with the proper node.
> + * The first page in every section holds node id, this is because we
> + * will need it in online_pages().
s/holds node id
/holds the node id
> +#ifdef CONFIG_DEBUG_VM
> + /*
> + * poison uninitialized struct pages in order to catch invalid flags
> + * combinations.
Please capitalize sentences properly.
> + */
> + memset(memmap, PAGE_POISON_PATTERN,
> + sizeof(struct page) * PAGES_PER_SECTION);
> +#endif
I'd suggest writing this into a single line:
memset(memmap, PAGE_POISON_PATTERN, sizeof(struct page)*PAGES_PER_SECTION);
(And ignore any checkpatch whinging - the line break didn't make it more
readable.)
With those details fixed, and assuming that this patch was tested:
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Thanks,
Ingo
next prev parent reply other threads:[~2018-02-16 9:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-15 16:59 [v4 0/6] optimize memory hotplug Pavel Tatashin
2018-02-15 16:59 ` [v4 1/6] mm/memory_hotplug: enforce block size aligned range check Pavel Tatashin
2018-02-15 16:59 ` [v4 2/6] x86/mm/memory_hotplug: determine block size based on the end of boot memory Pavel Tatashin
2018-02-15 16:59 ` [v4 3/6] mm: uninitialized struct page poisoning sanity checking Pavel Tatashin
2018-02-16 9:23 ` Ingo Molnar
2018-02-16 13:10 ` Pavel Tatashin
2018-02-15 16:59 ` [v4 4/6] mm/memory_hotplug: optimize probe routine Pavel Tatashin
2018-02-16 9:13 ` Ingo Molnar
2018-02-16 13:07 ` Pavel Tatashin
2018-02-19 13:23 ` Michal Hocko
2018-02-15 16:59 ` [v4 5/6] mm/memory_hotplug: don't read nid from struct page during hotplug Pavel Tatashin
2018-02-16 9:19 ` Ingo Molnar
2018-02-16 13:09 ` Pavel Tatashin
2018-02-19 13:37 ` Michal Hocko
2018-02-15 16:59 ` [v4 6/6] mm/memory_hotplug: optimize memory hotplug Pavel Tatashin
2018-02-16 9:30 ` Ingo Molnar [this message]
2018-02-16 13:12 ` Pavel Tatashin
2018-02-19 13:42 ` Michal Hocko
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