linux-kernel - Re: [patch 05/11] syslets: core code

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.64.0702150847420.10697@alien.or.mcafeemobile.com>
Date:	Thu, 15 Feb 2007 09:05:13 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Evgeniy Polyakov <johnpol@....mipt.ru>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 05/11] syslets: core code

On Thu, 15 Feb 2007, Linus Torvalds wrote:

> I don't think the "atom" approach is bad per se. I think it could be fine 
> to have some state information in user space. It's just that I think 
> complex interfaces that people largely won't even use is a big mistake. We 
> should concentrate on usability first, and some excessive cleverness 
> really isn't a big advantage.
> 
> Being able to do a "open + stat" looks like a fine thing. But I doubt 
> you'll see a lot of other combinations.

I actually think that building chains of syscalls bring you back to a 
multithreaded solution. Why? Because suddendly the service thread become 
from servicing a syscall (with possible cachehit optimization), to 
servicing a whole session. So the number of service threads needed (locked 
down by a chain) becomes big because requests goes from being short-lived 
syscalls to long-lived chains of them. Think about the trivial web server, 
and think about a chain that does open->fstat->sendhdrs->sendfile after an 
accept. What's the difference with a multithreaded solution that does 
accept->clone and execute the above code in the new thread? Nada, NIL. 
Actually, there is a difference. The standard multithreaded function is 
easier to code in C than with the complex atoms chains. The number of 
service thread becomes suddendly proportional to the number of active 
sessions.
The more I look at this, the more I think that async_submit should submit 
simple syscalls, or an array of them (unrelated/parallel).

- Davide

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/