From: John Hubbard <jhubbard@nvidia.com>
To: Leonardo Bras <leonardo@linux.ibm.com>,
<linuxppc-dev@lists.ozlabs.org>, <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Cc: Dan Williams <dan.j.williams@intel.com>,
Arnd Bergmann <arnd@arndb.de>, Jason Gunthorpe <jgg@ziepe.ca>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
YueHaibing <yuehaibing@huawei.com>,
Nicholas Piggin <npiggin@gmail.com>,
"Mike Rapoport" <rppt@linux.ibm.com>,
Keith Busch <keith.busch@intel.com>,
"Richard Fontana" <rfontana@redhat.com>,
Paul Mackerras <paulus@samba.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Ganesh Goudar <ganeshgr@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ira Weiny <ira.weiny@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Allison Randal" <allison@lohutok.net>
Subject: Re: [PATCH v2 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing
Date: Mon, 23 Sep 2019 13:26:48 -0700 [thread overview]
Message-ID: <b72cb1db-c341-4963-1a8b-ae71fe936458@nvidia.com> (raw)
In-Reply-To: <c64d34118542d5c2d31b8f6b7802d2a29dac71ef.camel@linux.ibm.com>
On 9/23/19 1:23 PM, Leonardo Bras wrote:
> On Mon, 2019-09-23 at 12:58 -0700, John Hubbard wrote:
>>
>> CPU 0 CPU 1
>> ------ --------------
>> READ(pte) (re-ordered at run time)
>> atomic_inc(val) (no run-time memory barrier!)
>>
>> pmd_clear(pte)
>> if (val)
>> run_on_all_cpus(): IPI
>> local_irq_disable() (also not a mem barrier)
>>
>> if(pte)
>> walk page tables
>
> Let me see if I can understand,
> On most patches, it would be:
>
> CPU 0 CPU 1
> ------ --------------
> ptep = __find_linux_pte
> (re-ordered at run time)
> atomic_inc(val)
> pmd_clear(pte)
> smp_mb()
> if (val)
> run_on_all_cpus(): IPI
> local_irq_disable()
>
> if(ptep)
> pte = *ptep;
>
> Is that what you meant?
>
>
Yes.
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2019-09-23 20:26 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190920195047.7703-1-leonardo@linux.ibm.com>
[not found] ` <20190920195047.7703-12-leonardo@linux.ibm.com>
[not found] ` <1b39eaa7-751d-40bc-d3d7-41aaa15be42a@nvidia.com>
[not found] ` <24863d8904c6e05e5dd48cab57db4274675ae654.camel@linux.ibm.com>
2019-09-21 0:48 ` [PATCH v2 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing John Hubbard
2019-09-23 17:25 ` Leonardo Bras
2019-09-23 18:14 ` John Hubbard
2019-09-23 19:40 ` Leonardo Bras
2019-09-23 19:58 ` John Hubbard
2019-09-23 20:23 ` Leonardo Bras
2019-09-23 20:26 ` John Hubbard [this message]
[not found] ` <20190920195047.7703-4-leonardo@linux.ibm.com>
2019-09-23 20:27 ` [PATCH v2 03/11] mm/gup: Applies counting method to monitor gup_pgd_range John Hubbard
2019-09-23 21:01 ` Leonardo Bras
2019-09-23 21:09 ` John Hubbard
[not found] ` <20190920195047.7703-3-leonardo@linux.ibm.com>
2019-09-23 20:39 ` [PATCH v2 02/11] asm-generic/pgtable: Adds dummy functions to monitor lockless pgtable walks John Hubbard
2019-09-23 20:48 ` Leonardo Bras
2019-09-23 20:53 ` John Hubbard
[not found] ` <20190920195047.7703-2-leonardo@linux.ibm.com>
2019-09-23 20:42 ` [PATCH v2 01/11] powerpc/mm: Adds counting method " John Hubbard
2019-09-23 20:50 ` Leonardo Bras
[not found] ` <20190920195047.7703-9-leonardo@linux.ibm.com>
2019-09-23 20:47 ` [PATCH v2 08/11] powerpc/kvm/book3s_hv: Applies counting method to monitor lockless pgtbl walks John Hubbard
[not found] ` <1f5d9380418ad8bb90c6bbdac34716c650b917a0.camel@linux.ibm.com>
2019-09-20 21:24 ` [PATCH v2 00/11] Introduces new count-based method for monitoring lockless pagetable wakls John Hubbard
2019-09-23 20:51 ` John Hubbard
2019-09-23 20:58 ` Leonardo Bras
2019-09-24 21:23 [PATCH v2 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing Leonardo Bras
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