From: Cyrill Gorcunov <gorcunov@gmail.com>
To: david@lang.hm
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Pavel Emelyanov <xemul@parallels.com>,
Andrey Vagin <avagin@openvz.org>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Glauber Costa <glommer@parallels.com>,
Andi Kleen <andi@firstfloor.org>, Tejun Heo <tj@kernel.org>,
Matt Helsley <matthltc@us.ibm.com>,
Pekka Enberg <penberg@kernel.org>,
Eric Dumazet <eric.dumazet@gmail.com>,
Vasiliy Kulikov <segoon@openwall.com>,
Andrew Morton <akpm@linux-foundation.org>,
Valdis.Kletnieks@vt.edu
Subject: Re: [RFC] syscalls, x86: Add __NR_kcmp syscall
Date: Thu, 19 Jan 2012 02:49:56 +0400 [thread overview]
Message-ID: <20120118224956.GF15652@moon> (raw)
In-Reply-To: <alpine.DEB.2.02.1201181404480.6780@asgard.lang.hm>
On Wed, Jan 18, 2012 at 02:05:31PM -0800, david@lang.hm wrote:
...
> >>
> >>Why on Earth would user space need to know which order in memory certain
> >>kernel objects are?
> >
> >For checkpoint restart and for some other kinds of introspection what is
> >needed is a comparison function to see if two processes share the same
> >object. The most interesting of these objects from a checkpoint restart case
> >are file descriptors, and there can be a lot of file descriptors.
> >
> >The order in memory does not matter. What does matter is that the
> >comparison function return some ordering between objects. The algorithm
> >for figuring out of N items which of them are duplicates is O(N^2) if
> >the comparison function can only return equal or not equal. The
> >algorithm for finding duplications is only O(NlogN) if the comparison
> >function will return an ordering among the objects.
>
> so what you really want is a syscall that can take a list of objects
> instead of having to do a syscall per object. right?
>
It doesn't matter. Even if we take a list of objects the kernel either
should return us some ordering info or find duplicates, in any case it
makes things more complex i think. So we wanted to bring some minimum
into kernel leaving the rest of work to user-space.
(and, btw, Eric, I'm really sorry that I didn't mentioned this sorting
problem at the very first email).
Cyrill
next prev parent reply other threads:[~2012-01-18 22:50 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-17 14:27 [RFC] syscalls, x86: Add __NR_kcmp syscall Cyrill Gorcunov
2012-01-17 14:38 ` Alexey Dobriyan
2012-01-17 14:44 ` Cyrill Gorcunov
2012-01-17 18:47 ` H. Peter Anvin
2012-01-17 21:15 ` Cyrill Gorcunov
2012-01-17 21:40 ` Eric W. Biederman
2012-01-18 5:07 ` Pavel Emelyanov
2012-01-17 21:35 ` Eric W. Biederman
2012-01-18 8:01 ` Cyrill Gorcunov
2012-01-18 9:12 ` KOSAKI Motohiro
2012-01-18 9:19 ` Pavel Emelyanov
2012-01-18 9:23 ` KOSAKI Motohiro
2012-01-18 11:57 ` Cyrill Gorcunov
2012-01-18 16:46 ` KOSAKI Motohiro
2012-01-18 17:20 ` Cyrill Gorcunov
2012-01-18 22:05 ` david
2012-01-18 22:49 ` Cyrill Gorcunov [this message]
2012-01-18 23:29 ` Eric W. Biederman
2012-01-19 6:55 ` Cyrill Gorcunov
2012-01-20 3:16 ` Eric W. Biederman
2012-01-20 8:40 ` Cyrill Gorcunov
2012-01-20 9:02 ` Cyrill Gorcunov
2012-01-20 14:51 ` H. Peter Anvin
2012-01-20 16:29 ` Cyrill Gorcunov
2012-01-20 16:57 ` H. Peter Anvin
2012-01-20 18:19 ` Cyrill Gorcunov
2012-01-20 18:22 ` Cyrill Gorcunov
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=20120118224956.GF15652@moon \
--to=gorcunov@gmail.com \
--cc=Valdis.Kletnieks@vt.edu \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=andi@firstfloor.org \
--cc=avagin@openvz.org \
--cc=david@lang.hm \
--cc=ebiederm@xmission.com \
--cc=eric.dumazet@gmail.com \
--cc=glommer@parallels.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=matthltc@us.ibm.com \
--cc=mingo@elte.hu \
--cc=penberg@kernel.org \
--cc=segoon@openwall.com \
--cc=tglx@linutronix.de \
--cc=tj@kernel.org \
--cc=xemul@parallels.com \
/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).