From: Peter Zijlstra <peterz@infradead.org>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "kirill@shutemov.name" <kirill@shutemov.name>,
"adobriyan@gmail.com" <adobriyan@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"rppt@kernel.org" <rppt@kernel.org>,
"rostedt@goodmis.org" <rostedt@goodmis.org>,
"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"luto@kernel.org" <luto@kernel.org>,
"rppt@linux.ibm.com" <rppt@linux.ibm.com>,
"bp@alien8.de" <bp@alien8.de>, "arnd@arndb.de" <arnd@arndb.de>
Subject: Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings
Date: Mon, 28 Oct 2019 22:00:52 +0100 [thread overview]
Message-ID: <20191028210052.GM4643@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <0a35765f7412937c1775daa05177b20113760aee.camel@intel.com>
On Mon, Oct 28, 2019 at 07:59:25PM +0000, Edgecombe, Rick P wrote:
> On Mon, 2019-10-28 at 14:55 +0100, Peter Zijlstra wrote:
> > On Mon, Oct 28, 2019 at 04:16:23PM +0300, Kirill A. Shutemov wrote:
> >
> > > I think active use of this feature will lead to performance degradation of
> > > the system with time.
> > >
> > > Setting a single 4k page non-present in the direct mapping will require
> > > splitting 2M or 1G page we usually map direct mapping with. And it's one
> > > way road. We don't have any mechanism to map the memory with huge page
> > > again after the application has freed the page.
> >
> > Right, we recently had a 'bug' where ftrace triggered something like
> > this and facebook ran into it as a performance regression. So yes, this
> > is a real concern.
>
> Don't e/cBPF filters also break the direct map down to 4k pages when calling
> set_memory_ro() on the filter for 64 bit x86 and arm?
>
> I've been wondering if the page allocator should make some effort to find a
> broken down page for anything that can be known will have direct map permissions
> changed (or if it already groups them somehow). But also, why any potential
> slowdown of 4k pages on the direct map hasn't been noticed for apps that do a
> lot of insertions and removals of BPF filters, if this is indeed the case.
That should be limited to the module range. Random data maps could
shatter the world.
next prev parent reply other threads:[~2019-10-28 21:01 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-27 10:17 [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Mike Rapoport
2019-10-27 10:17 ` Mike Rapoport
2019-10-28 12:31 ` Kirill A. Shutemov
2019-10-28 13:00 ` Mike Rapoport
2019-10-28 13:16 ` Kirill A. Shutemov
2019-10-28 13:55 ` Peter Zijlstra
2019-10-28 19:59 ` Edgecombe, Rick P
2019-10-28 21:00 ` Peter Zijlstra [this message]
2019-10-29 17:27 ` Edgecombe, Rick P
2019-10-30 10:04 ` Peter Zijlstra
2019-10-30 15:35 ` Alexei Starovoitov
2019-10-30 18:39 ` Peter Zijlstra
2019-10-30 18:52 ` Alexei Starovoitov
2019-10-30 17:48 ` Edgecombe, Rick P
2019-10-30 17:58 ` Dave Hansen
2019-10-30 18:01 ` Dave Hansen
2019-10-29 5:43 ` Dan Williams
2019-10-29 6:43 ` Kirill A. Shutemov
2019-10-29 8:56 ` Peter Zijlstra
2019-10-29 11:00 ` Kirill A. Shutemov
2019-10-29 12:39 ` AMD TLB errata, (Was: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings) Peter Zijlstra
2019-11-15 14:12 ` Tom Lendacky
2019-11-15 14:31 ` Peter Zijlstra
2019-10-29 19:43 ` [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Dan Williams
2019-10-29 20:07 ` Dave Hansen
2019-10-29 7:08 ` Christopher Lameter
2019-10-29 8:55 ` Mike Rapoport
2019-10-29 10:12 ` Christopher Lameter
2019-10-30 7:11 ` Mike Rapoport
2019-10-30 12:09 ` Christopher Lameter
2019-10-28 14:55 ` David Hildenbrand
2019-10-28 17:12 ` Dave Hansen
2019-10-28 17:32 ` Sean Christopherson
2019-10-28 18:08 ` Matthew Wilcox
2019-10-29 9:28 ` Mike Rapoport
2019-10-29 9:19 ` Mike Rapoport
2019-10-28 18:02 ` Andy Lutomirski
2019-10-29 11:02 ` David Hildenbrand
2019-10-30 8:15 ` Mike Rapoport
2019-10-30 8:19 ` David Hildenbrand
2019-10-31 19:16 ` Mike Rapoport
2019-10-31 21:52 ` Dan Williams
2019-10-27 10:30 ` Florian Weimer
2019-10-27 11:00 ` Mike Rapoport
2019-10-28 20:23 ` Florian Weimer
2019-10-29 9:01 ` Mike Rapoport
2019-10-28 20:44 ` Andy Lutomirski
2019-10-29 9:32 ` Mike Rapoport
2019-10-29 17:00 ` Andy Lutomirski
2019-10-30 8:40 ` Mike Rapoport
2019-10-30 21:28 ` Andy Lutomirski
2019-10-31 7:21 ` Mike Rapoport
2019-12-05 15:34 ` Mike Rapoport
2019-12-08 14:10 ` [PATCH] mm: extend memfd with ability to create secret memory kbuild test robot
2019-10-29 11:25 ` [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Reshetova, Elena
2019-10-29 15:13 ` Tycho Andersen
2019-10-29 17:03 ` Andy Lutomirski
2019-10-29 17:37 ` Alan Cox
2019-10-29 17:43 ` James Bottomley
2019-10-29 18:10 ` Andy Lutomirski
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=20191028210052.GM4643@worktop.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=jejb@linux.ibm.com \
--cc=kirill@shutemov.name \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=rick.p.edgecombe@intel.com \
--cc=rostedt@goodmis.org \
--cc=rppt@kernel.org \
--cc=rppt@linux.ibm.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/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).