From: Jia He <hejianet@gmail.com>
To: Daniel Vacek <neelx@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Mel Gorman <mgorman@suse.de>, Will Deacon <will.deacon@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Pavel Tatashin <pasha.tatashin@oracle.com>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
AKASHI Takahiro <takahiro.akashi@linaro.org>,
Gioh Kim <gi-oh.kim@profitbricks.com>,
Steven Sistare <steven.sistare@oracle.com>,
Eugeniu Rosca <erosca@de.adit-jv.com>,
Vlastimil Babka <vbabka@suse.cz>,
open list <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, James Morse <james.morse@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Steve Capper <steve.capper@arm.com>,
x86@kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kate Stewart <kstewart@linuxfoundation.org>,
Philippe Ombredanne <pombredanne@nexb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Kemi Wang <kemi.wang@intel.com>, Petr Tesarik <ptesarik@suse.com>,
YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Nikolay Borisov <nborisov@suse.com>,
Jia He <jia.he@hxt-semitech.com>
Subject: Re: [PATCH 1/4] mm: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn()
Date: Wed, 21 Mar 2018 20:28:18 +0800 [thread overview]
Message-ID: <3f208ebe-572f-f2f6-003e-5a9cf49bb92f@gmail.com> (raw)
In-Reply-To: <CACjP9X92M3izDD-1s1vY6n6Hx3mxqNqeM4f+T3RNnBo8kjP4Qg@mail.gmail.com>
On 3/21/2018 6:14 PM, Daniel Vacek Wrote:
> On Wed, Mar 21, 2018 at 9:09 AM, Jia He <hejianet@gmail.com> wrote:
>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>> where possible") optimized the loop in memmap_init_zone(). But there is
>> still some room for improvement. E.g. if pfn and pfn+1 are in the same
>> memblock region, we can simply pfn++ instead of doing the binary search
>> in memblock_next_valid_pfn.
> There is a revert-mm-page_alloc-skip-over-regions-of-invalid-pfns-where-possible.patch
> in -mm reverting b92df1de5d289c0b as it is fundamentally wrong by
> design causing system panics on some machines with rare but still
> valid mappings. Basically it skips valid pfns which are outside of
> usable memory ranges (outside of memblock memory regions).
Thanks for the infomation.
quote from you patch description:
>But given some specific memory mapping on x86_64 (or more generally
theoretically anywhere but on arm with CONFIG_HAVE_ARCH_PFN_VALID) > the
implementation also skips valid pfns which is plain wrong and causes >
'kernel BUG at mm/page_alloc.c:1389!'
Do you think memblock_next_valid_pfn can remain to be not reverted on
arm64 with CONFIG_HAVE_ARCH_PFN_VALID? Arm64 can benifit from this
optimization.
Cheers,
Jia
next prev parent reply other threads:[~2018-03-21 12:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-21 8:09 [PATCH RFC 0/4] optimize memblock_next_valid_pfn() and early_pfn_valid() Jia He
2018-03-21 8:09 ` [PATCH 1/4] mm: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() Jia He
2018-03-21 10:14 ` Daniel Vacek
2018-03-21 12:28 ` Jia He [this message]
2018-03-21 15:04 ` Daniel Vacek
2018-03-22 12:52 ` Eugeniu Rosca
2018-03-22 12:52 ` Eugeniu Rosca
2018-03-21 8:09 ` [PATCH 2/4] mm/memblock: introduce memblock_search_pfn_regions() Jia He
2018-03-21 10:14 ` Daniel Vacek
2018-03-21 12:04 ` Jia He
2018-03-21 8:09 ` [PATCH 3/4] arm64: introduce pfn_valid_region() Jia He
2018-03-21 8:09 ` [PATCH 4/4] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid() Jia He
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