From: Darren Hart <dvhltc@us.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Ian Jackson <ijackson@chiark.greenend.org.uk>,
Greg KH <gregkh@suse.de>, Ian Campbell <ijc@hellion.org.uk>,
linux-kernel@vger.kernel.org, stable@kernel.org,
stable-review@kernel.org, akpm@linux-foundation.org,
alan@lxorguk.ukuu.org.uk, Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [RFC] mlock/stack guard interaction fixup
Date: Mon, 23 Aug 2010 11:43:05 -0700 [thread overview]
Message-ID: <4C72C139.9090601@us.ibm.com> (raw)
In-Reply-To: <1282586385.2605.2119.camel@laptop>
On 08/23/2010 10:59 AM, Peter Zijlstra wrote:
> On Mon, 2010-08-23 at 10:34 -0700, Linus Torvalds wrote:
>> I suspect that if you use mlock for _any_ other reason than protecting
>> a particular very sensitive piece of information, you should use
>> mlockall(MCL_FUTURE). IOW, if you use mlock because you have realtime
>> issues, there is no excuse to ever use anything else, imho. And even
>> then, I guarantee that things like copy-on-write is going to be
>> "interesting".
>>
>> I realize that people hate mlockall() (and particularly MCL_FUTURE),
>> and yes, it's a bloated thing that you can't reasonably use on a large
>> process. But dammit, if you have RT issues, you shouldn't _have_ some
>> big bloated process. You should have a small statically linked server
>> that is RT, and nothing else.
>
> Us real-time people have been telling people to not use mlockall() at
> all.
Well, we have at least two camps of people here I guess. When people
come to me with unexplainable latencies, paging is one of the things we
check for, and mlockall() is a good way to test if avoiding that paging
will help them - so I have been known to recommend it on occasion.
> While small !glibc statically linked RT components using shared memory
> interfaces to !RT apps could work its not how people actually write
> their apps. They write big monolithic threaded apps where some threads
> are RT.
>
> [ in part because there doesn't seem to be a usable !glibc
> libpthread/librt implementation out there, in part because people use
> crap like Java-RT ]
Which is also missing some performance and functionality due to the lack
of complete pthread support for priority inheritance (and the complete
disinterest in fixing it by certain maintainers).
--
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
next prev parent reply other threads:[~2010-08-23 18:43 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-20 23:59 [RFC] mlock/stack guard interaction fixup Linus Torvalds
2010-08-21 0:20 ` Mike Snitzer
2010-08-21 0:54 ` Linus Torvalds
2010-08-21 11:56 ` Ian Campbell
2010-08-21 15:48 ` Linus Torvalds
2010-08-21 16:08 ` Sam Ravnborg
2010-08-23 16:34 ` Tony Luck
2010-08-22 6:57 ` Ian Campbell
2010-08-22 7:33 ` Ian Campbell
2010-08-22 9:55 ` Ian Campbell
2010-08-22 16:43 ` Linus Torvalds
2010-08-22 17:25 ` Greg KH
2010-08-22 18:21 ` Linus Torvalds
2010-08-22 19:04 ` Greg KH
2010-08-23 9:22 ` Peter Zijlstra
2010-08-23 15:42 ` ijackson
2010-08-23 16:25 ` Peter Zijlstra
2010-08-23 17:18 ` Ian Jackson
2010-08-23 17:34 ` Linus Torvalds
2010-08-23 17:53 ` Peter Zijlstra
2010-08-23 17:59 ` Peter Zijlstra
2010-08-23 18:43 ` Darren Hart [this message]
2010-08-23 18:50 ` Jeremy Fitzhardinge
2010-08-23 19:07 ` Peter Zijlstra
2010-08-23 19:23 ` Jeremy Fitzhardinge
2010-08-23 19:26 ` Peter Zijlstra
2010-08-23 19:54 ` Jeremy Fitzhardinge
2010-08-24 7:08 ` Peter Zijlstra
2010-08-24 7:20 ` Peter Zijlstra
2010-08-23 19:03 ` Ian Campbell
2010-08-23 17:40 ` Peter Zijlstra
2010-08-23 18:53 ` Jeremy Fitzhardinge
2010-08-25 8:28 ` [Stable-review] " Stefan Bader
2010-08-23 9:00 ` Peter Zijlstra
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