From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>,
Leonardo Bras <leonardo@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org,
linux-mm@kvack.org,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Paul Mackerras" <paulus@samba.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Arnd Bergmann" <arnd@arndb.de>,
"Christophe Leroy" <christophe.leroy@c-s.fr>,
"Nicholas Piggin" <npiggin@gmail.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mahesh Salgaonkar" <mahesh@linux.vnet.ibm.com>,
"Reza Arbab" <arbab@linux.ibm.com>,
"Santosh Sivaraj" <santosh@fossix.org>,
"Balbir Singh" <bsingharora@gmail.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Mike Rapoport" <rppt@linux.ibm.com>,
"Allison Randal" <allison@lohutok.net>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Dan Williams" <dan.j.williams@intel.com>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Christoph Lameter" <cl@linux.com>,
"Logan Gunthorpe" <logang@deltatee.com>,
"Andrey Ryabinin" <aryabinin@virtuozzo.com>,
"Alexey Dobriyan" <adobriyan@gmail.com>,
"Souptick Joarder" <jrdr.linux@gmail.com>,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
"Ralph Campbell" <rcampbell@nvidia.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Jann Horn" <jannh@google.com>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"Ingo Molnar" <mingo@kernel.org>,
"Christian Brauner" <christian.brauner@ubuntu.com>,
"Michal Hocko" <mhocko@suse.com>,
"Elena Reshetova" <elena.reshetova@intel.com>,
"Roman Gushchin" <guro@fb.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Dmitry V. Levin" <ldv@altlinux.org>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Song Liu" <songliubraving@fb.com>,
"Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>,
"Ira Weiny" <ira.weiny@intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Keith Busch" <keith.busch@intel.com>
Subject: Re: [PATCH v5 01/11] asm-generic/pgtable: Adds generic functions to monitor lockless pgtable walks
Date: Sat, 5 Oct 2019 14:05:29 +0530 [thread overview]
Message-ID: <651856af-30de-15ad-2312-158f3ad5292e@linux.ibm.com> (raw)
In-Reply-To: <20191003115141.GJ4581@hirez.programming.kicks-ass.net>
On 10/3/19 5:21 PM, Peter Zijlstra wrote:
> On Thu, Oct 03, 2019 at 09:11:45AM +0200, Peter Zijlstra wrote:
>> On Wed, Oct 02, 2019 at 10:33:15PM -0300, Leonardo Bras wrote:
....
>
> And I still think all that wrong, you really shouldn't need to wait on
> munmap().
>
I do have a patch that does something like that.
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR_FULL
+static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
+ unsigned long address, pmd_t *pmdp,
+ int full)
+{
+ bool serialize = true;
+ /*
+ * We don't need to serialze against a lockless page table walk if
+ * we are clearing the pmd due to task exit. For regular mnumap, we
+ * still need to serialize due the possibility of MADV_DONTNEED running
+ * parallel to a page fault which can convert a THP pte entry to a
+ * pointer to level 4 table.
+ * Here MADV_DONTNEED is removing the THP entry and the fault is filling
+ * a level 4 pte.
+ */
+ if (full == 1)
+ serialize = false;
+ return __pmdp_huge_get_and_clear(mm, address, pmdp, serialize);
}
if it is a fullmm flush we can skip that serialize, But for everything
else we need to serialize. MADV_DONTNEED is another case. I haven't sent
this yet, because I was trying to look at what it takes to switch that
MADV variant to take mmap_sem in write mode.
MADV_DONTNEED has caused us multiple issues due to the fact that it can
run in parallel to page fault. I am not sure whether we have a
known/noticeable performance gain in allowing that with mmap_sem held in
read mode.
-aneesh
next prev parent reply other threads:[~2019-10-05 8:36 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 [this message]
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
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
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=651856af-30de-15ad-2312-158f3ad5292e@linux.ibm.com \
--to=aneesh.kumar@linux.ibm.com \
--cc=aarcange@redhat.com \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=allison@lohutok.net \
--cc=arbab@linux.ibm.com \
--cc=arnd@arndb.de \
--cc=aryabinin@virtuozzo.com \
--cc=b.zolnierkie@samsung.com \
--cc=benh@kernel.crashing.org \
--cc=brouer@redhat.com \
--cc=bsingharora@gmail.com \
--cc=christian.brauner@ubuntu.com \
--cc=christophe.leroy@c-s.fr \
--cc=cl@linux.com \
--cc=dan.j.williams@intel.com \
--cc=dave@stgolabs.net \
--cc=elena.reshetova@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=guro@fb.com \
--cc=ira.weiny@intel.com \
--cc=jannh@google.com \
--cc=jgg@ziepe.ca \
--cc=jglisse@redhat.com \
--cc=jhubbard@nvidia.com \
--cc=jrdr.linux@gmail.com \
--cc=keith.busch@intel.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kvm-ppc@vger.kernel.org \
--cc=ldv@altlinux.org \
--cc=leonardo@linux.ibm.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=logang@deltatee.com \
--cc=mahesh@linux.vnet.ibm.com \
--cc=mathieu.desnoyers@efficios.com \
--cc=mhocko@suse.com \
--cc=mingo@kernel.org \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
--cc=paulus@samba.org \
--cc=peterz@infradead.org \
--cc=rcampbell@nvidia.com \
--cc=rppt@linux.ibm.com \
--cc=santosh@fossix.org \
--cc=songliubraving@fb.com \
--cc=tglx@linutronix.de \
--cc=vbabka@suse.cz \
--cc=viro@zeniv.linux.org.uk \
/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).