linux-kernel - Re: kvm aio wishlist

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]

Date:	Tue, 25 Nov 2008 17:56:13 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Avi Kivity <avi@...hat.com>
Cc:	suparna@...ibm.com, Zach Brown <zach.brown@...cle.com>,
	linux-aio@...ck.org, Jeff Moyer <jmoyer@...hat.com>,
	Anthony Liguori <aliguori@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: kvm aio wishlist


* Avi Kivity <avi@...hat.com> wrote:

> Ingo Molnar wrote:
>>   
>>> Perhaps a variant of syslet, that is kernel-only, and does:
>>>
>>> - always allocate a new kernel stack at io_submit() time, but not a   
>>> new thread
>>>     
>>
>> such a N:M threading design is a loss - sooner or later we arrive to a  
>> point where people actually start using it and then we want to  
>> load-balance and schedule these entities.
>>   
>
> It's only N:M as long as its nonblocking.  If it blocks it becomes 1:1  
> again.  If it doesn't, it's probably faster to do things on the same  
> cache as the caller.
>
>> So i'd suggest the kthread based async engine i wrote for syslets. It  
>> worked well and for kernel-only entities it schedules super-fast - it  
>> can do up to 20 million events per second on a 16-way box i'm testing  
>> on. The objections about syslets were not related to the scheduling of  
>> it but were mostly about the userspace API/ABI: you dont have to use  
>> that.
>
> I'd love to have something :)
>
> I guess any cache and latency considerations could be fixed if
> - we schedule a syslet for the first time when the thread that launched  
> it exits to userspace
> - we queue it on the current cpu's runqueue
>
> In that case, for the nonblocking case syslets and fibrils would 
> have very similar performance.

yes. Hence given that fibrills have various tradeoffs, we should do 
the syslet thread pool. The code is there and it works :)

	Ingo
--
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/