From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>,
Alexander Duyck <alexander.duyck@gmail.com>
Cc: yang.zhang.wz@gmail.com, pagupta@redhat.com, kvm@vger.kernel.org,
david@redhat.com, catalin.marinas@arm.com, mhocko@kernel.org,
linux-mm@kvack.org, will@kernel.org, aarcange@redhat.com,
virtio-dev@lists.oasis-open.org, mst@redhat.com,
willy@infradead.org, wei.w.wang@intel.com, ying.huang@intel.com,
riel@surriel.com, dan.j.williams@intel.com,
lcapitulino@redhat.com, linux-arm-kernel@lists.infradead.org,
osalvador@suse.de, nitesh@redhat.com, konrad.wilk@oracle.com,
dave.hansen@intel.com, linux-kernel@vger.kernel.org,
pbonzini@redhat.com, akpm@linux-foundation.org,
fengguang.wu@intel.com, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling
Date: Mon, 09 Sep 2019 08:12:12 -0700 [thread overview]
Message-ID: <f2fc0cda183098aa9b3b071ff0f49249f6d94bd5.camel@linux.intel.com> (raw)
In-Reply-To: <20190909090701.7ebz4foxyu3rxzvc@box>
On Mon, 2019-09-09 at 12:07 +0300, Kirill A. Shutemov wrote:
> On Sat, Sep 07, 2019 at 10:25:12AM -0700, Alexander Duyck wrote:
> > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> >
> > Change the logic used to generate randomness in the suffle path so that we
>
> Typo.
>
> > can avoid cache line bouncing. The previous logic was sharing the offset
> > and entropy word between all CPUs. As such this can result in cache line
> > bouncing and will ultimately hurt performance when enabled.
> >
> > To resolve this I have moved to a per-cpu logic for maintaining a unsigned
> > long containing some amount of bits, and an offset value for which bit we
> > can use for entropy with each call.
> >
> > Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> > ---
> > mm/shuffle.c | 33 +++++++++++++++++++++++----------
> > 1 file changed, 23 insertions(+), 10 deletions(-)
> >
> > diff --git a/mm/shuffle.c b/mm/shuffle.c
> > index 3ce12481b1dc..9ba542ecf335 100644
> > --- a/mm/shuffle.c
> > +++ b/mm/shuffle.c
> > @@ -183,25 +183,38 @@ void __meminit __shuffle_free_memory(pg_data_t *pgdat)
> > shuffle_zone(z);
> > }
> >
> > +struct batched_bit_entropy {
> > + unsigned long entropy_bool;
> > + int position;
> > +};
> > +
> > +static DEFINE_PER_CPU(struct batched_bit_entropy, batched_entropy_bool);
> > +
> > void add_to_free_area_random(struct page *page, struct free_area *area,
> > int migratetype)
> > {
> > - static u64 rand;
> > - static u8 rand_bits;
> > + struct batched_bit_entropy *batch;
> > + unsigned long entropy;
> > + int position;
> >
> > /*
> > - * The lack of locking is deliberate. If 2 threads race to
> > - * update the rand state it just adds to the entropy.
> > + * We shouldn't need to disable IRQs as the only caller is
> > + * __free_one_page and it should only be called with the zone lock
> > + * held and either from IRQ context or with local IRQs disabled.
> > */
> > - if (rand_bits == 0) {
> > - rand_bits = 64;
> > - rand = get_random_u64();
> > + batch = raw_cpu_ptr(&batched_entropy_bool);
> > + position = batch->position;
> > +
> > + if (--position < 0) {
> > + batch->entropy_bool = get_random_long();
> > + position = BITS_PER_LONG - 1;
> > }
> >
> > - if (rand & 1)
> > + batch->position = position;
> > + entropy = batch->entropy_bool;
> > +
> > + if (1ul & (entropy >> position))
>
> Maybe something like this would be more readble:
>
> if (entropy & BIT(position))
>
> > add_to_free_area(page, area, migratetype);
> > else
> > add_to_free_area_tail(page, area, migratetype);
> > - rand_bits--;
> > - rand >>= 1;
> > }
> >
> >
Thanks for the review. I will update these two items for v10.
- Alex
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-09-09 15:12 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-07 17:25 [PATCH v9 0/8] stg mail -e --version=v9 \ Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling Alexander Duyck
2019-09-09 8:14 ` David Hildenbrand
2019-09-09 15:11 ` Alexander Duyck
2019-09-10 12:11 ` Michal Hocko
2019-09-10 22:14 ` Alexander Duyck
2019-09-10 22:11 ` Alexander Duyck
2019-09-09 9:07 ` Kirill A. Shutemov
2019-09-09 15:12 ` Alexander Duyck [this message]
2019-09-07 17:25 ` [PATCH v9 2/8] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-09-09 8:19 ` David Hildenbrand
2019-09-09 9:47 ` Kirill A. Shutemov
2019-09-09 15:22 ` Alexander Duyck
2019-09-09 15:35 ` Kirill A. Shutemov
2019-09-09 15:37 ` Alexander Duyck
2019-09-09 16:43 ` Alexander Duyck
2019-09-09 17:00 ` Kirill A. Shutemov
2019-09-10 12:20 ` Michal Hocko
2019-09-10 14:48 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 3/8] mm: Move set/get_pcppage_migratetype to mmzone.h Alexander Duyck
2019-09-09 8:22 ` David Hildenbrand
2019-09-09 9:56 ` Kirill A. Shutemov
2019-09-09 18:01 ` Alexander Duyck
2019-09-09 18:12 ` Alexander Duyck
2019-09-10 12:23 ` Michal Hocko
2019-09-10 14:46 ` Alexander Duyck
2019-09-10 17:45 ` Michal Hocko
2019-09-10 20:26 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 4/8] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-09-10 12:27 ` Michal Hocko
2019-09-07 17:25 ` [PATCH v9 5/8] arm64: Move hugetlb related definitions out of pgtable.h to page-defs.h Alexander Duyck
2019-09-09 8:52 ` David Hildenbrand
2019-09-09 15:27 ` Alexander Duyck
2019-09-17 17:48 ` Will Deacon
2019-09-17 20:07 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 6/8] mm: Introduce Reported pages Alexander Duyck
2019-09-09 14:42 ` Kirill A. Shutemov
2019-09-09 16:25 ` Alexander Duyck
2019-09-09 16:33 ` Kirill A. Shutemov
2019-09-07 17:26 ` [PATCH v9 7/8] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-09-09 8:59 ` David Hildenbrand
2019-09-09 15:31 ` Alexander Duyck
2019-09-07 17:26 ` [PATCH v9 8/8] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
2019-09-07 17:34 ` [PATCH v9 0/8] mm / virtio: Provide support for unused page reporting Alexander Duyck
2019-09-10 12:42 ` [PATCH v9 0/8] stg mail -e --version=v9 \ Michal Hocko
2019-09-10 14:42 ` Alexander Duyck
2019-09-10 14:47 ` Michal Hocko
2019-09-10 16:05 ` Alexander Duyck
2019-09-10 16:18 ` [virtio-dev] " Dr. David Alan Gilbert
2019-09-10 16:22 ` David Hildenbrand
2019-09-11 9:23 ` Michael S. Tsirkin
2019-09-11 9:50 ` David Hildenbrand
2019-09-10 17:52 ` Michal Hocko
2019-09-10 18:00 ` Michal Hocko
2019-09-10 20:37 ` Alexander Duyck
2019-09-10 21:23 ` Alexander Duyck
2019-09-11 11:36 ` Michal Hocko
2019-09-11 11:47 ` David Hildenbrand
2019-09-11 12:08 ` Michael S. Tsirkin
2019-09-11 12:19 ` Michal Hocko
2019-09-11 12:25 ` Michal Hocko
2019-09-11 12:42 ` David Hildenbrand
2019-09-11 12:54 ` Michal Hocko
2019-09-11 13:03 ` David Hildenbrand
2019-09-11 13:20 ` Michal Hocko
2019-09-11 13:51 ` Michal Hocko
2019-09-11 16:09 ` David Hildenbrand
2019-09-12 7:16 ` Michal Hocko
2019-09-12 7:47 ` David Hildenbrand
2019-09-12 9:26 ` Michal Hocko
2019-09-12 12:00 ` Nitesh Narayan Lal
2019-09-11 14:03 ` Nitesh Narayan Lal
2019-09-11 16:02 ` David Hildenbrand
2019-09-11 13:19 ` Nitesh Narayan Lal
2019-09-11 12:55 ` Nitesh Narayan Lal
2019-09-11 15:12 ` Alexander Duyck
2019-09-12 9:19 ` Michal Hocko
2019-09-12 10:24 ` Kirill A. Shutemov
2019-09-12 11:11 ` Michal Hocko
2019-09-12 15:42 ` Alexander Duyck
2019-09-12 16:35 ` Mel Gorman
2019-09-12 17:48 ` Alexander Duyck
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=f2fc0cda183098aa9b3b071ff0f49249f6d94bd5.camel@linux.intel.com \
--to=alexander.h.duyck@linux.intel.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=alexander.duyck@gmail.com \
--cc=catalin.marinas@arm.com \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@intel.com \
--cc=david@redhat.com \
--cc=fengguang.wu@intel.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=konrad.wilk@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=lcapitulino@redhat.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mst@redhat.com \
--cc=nitesh@redhat.com \
--cc=osalvador@suse.de \
--cc=pagupta@redhat.com \
--cc=pbonzini@redhat.com \
--cc=riel@surriel.com \
--cc=virtio-dev@lists.oasis-open.org \
--cc=wei.w.wang@intel.com \
--cc=will@kernel.org \
--cc=willy@infradead.org \
--cc=yang.zhang.wz@gmail.com \
--cc=ying.huang@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).