From: Christopher Lameter <cl@linux.com>
To: Leonardo Bras <leonardo@linux.ibm.com>
Cc: "Song Liu" <songliubraving@fb.com>,
"Michal Hocko" <mhocko@suse.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
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linux-arch@vger.kernel.org,
"Santosh Sivaraj" <santosh@fossix.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
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"Andrew Morton" <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org, "Roman Gushchin" <guro@fb.com>,
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"Al Viro" <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v5 02/11] powerpc/mm: Adds counting method to monitor lockless pgtable walks
Date: Tue, 8 Oct 2019 17:43:10 +0000 (UTC) [thread overview]
Message-ID: <alpine.DEB.2.21.1910081741460.2923@www.lameter.com> (raw)
In-Reply-To: <6e8877bff034603e75b35599797a39d9bc4840f1.camel@linux.ibm.com>
On Tue, 8 Oct 2019, Leonardo Bras wrote:
> > You are creating contention on a single exclusive cacheline. Doesnt this
> > defeat the whole purpose of the lockless page table walk? Use mmap_sem or
> > so should cause the same performance regression?
>
> Sorry, I did not understand that question.
> I mean, this is just a refcount and never causes a lock.
Locks also use atomic operations like a refcount increment. Both require
the cacheline to be in exclusive state. So the impact is very similar.
next prev parent reply other threads:[~2019-10-08 17:43 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 1:33 [PATCH v5 00/11] Introduces new count-based method for tracking lockless pagetable walks Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 01/11] asm-generic/pgtable: Adds generic functions to monitor lockless pgtable walks Leonardo Bras
2019-10-03 7:11 ` Peter Zijlstra
2019-10-03 11:51 ` Peter Zijlstra
2019-10-03 20:40 ` John Hubbard
2019-10-04 11:24 ` Peter Zijlstra
2019-10-03 21:24 ` Leonardo Bras
2019-10-04 11:28 ` Peter Zijlstra
2019-10-09 18:09 ` Leonardo Bras
2019-10-05 8:35 ` Aneesh Kumar K.V
2019-10-08 14:47 ` Kirill A. Shutemov
2019-10-03 1:33 ` [PATCH v5 02/11] powerpc/mm: Adds counting method " Leonardo Bras
2019-10-08 15:11 ` Christopher Lameter
2019-10-08 17:13 ` Leonardo Bras
2019-10-08 17:43 ` Christopher Lameter [this message]
2019-10-08 18:02 ` Leonardo Bras
2019-10-08 18:27 ` Christopher Lameter
2019-10-03 1:33 ` [PATCH v5 03/11] mm/gup: Applies counting method to monitor gup_pgd_range Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 04/11] powerpc/mce_power: Applies counting method to monitor lockless pgtbl walks Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 05/11] powerpc/perf: " Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 06/11] powerpc/mm/book3s64/hash: " Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 07/11] powerpc/kvm/e500: " Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 08/11] powerpc/kvm/book3s_hv: " Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 09/11] powerpc/kvm/book3s_64: " Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 10/11] mm/Kconfig: Adds config option to track lockless pagetable walks Leonardo Bras
2019-10-03 2:08 ` Qian Cai
2019-10-03 19:04 ` Leonardo Bras
2019-10-03 19:08 ` Leonardo Bras
2019-10-03 7:44 ` Peter Zijlstra
2019-10-03 20:40 ` Leonardo Bras
2019-10-03 1:33 ` [PATCH v5 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing Leonardo Bras
2019-10-03 7:29 ` [PATCH v5 00/11] Introduces new count-based method for tracking lockless pagetable walks Peter Zijlstra
2019-10-03 20:36 ` Leonardo Bras
2019-10-03 20:49 ` John Hubbard
2019-10-03 21:38 ` Leonardo Bras
2019-10-04 11:42 ` Peter Zijlstra
2019-10-04 12:57 ` Peter Zijlstra
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