linux-kernel - Re: The performance and behaviour of the anti-fragmentation related patches

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.4.64.0703020015080.14651@schroedinger.engr.sgi.com>
Date:	Fri, 2 Mar 2007 00:21:49 -0800 (PST)
From:	Christoph Lameter <clameter@...r.sgi.com>
To:	Nick Piggin <npiggin@...e.de>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@...net.ie>, mingo@...e.hu,
	jschopp@...tin.ibm.com, arjan@...radead.org,
	torvalds@...ux-foundation.org, mbligh@...igh.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: The performance and behaviour of the anti-fragmentation related
 patches

On Fri, 2 Mar 2007, Nick Piggin wrote:

> > If there are billions of pages in the system and we are allocating and 
> > deallocating then pages need to be aged. If there are just few pages 
> > freeable then we run into issues.
> 
> page writeout and vmscan don't work too badly. What are the issues?

Slow downs up to livelocks with large memory configurations.

> So what problems that you commonly see now? Some of us here don't
> have 4TB of memory, so you actually have to tell us ;)

Oh just run a 32GB SMP system with sparsely freeable pages and lots of 
allocs and frees and you will see it too. F.e try Linus tree and mlock 
a large portion of the memory and then see the fun starting. See also 
Rik's list of pathological cases on this.

> How did you come up with that 2MB number?

Huge page size. The only basic choice on x86_64

> Anyway, we have hugetlbfs for things like that.

Good to know that direct io works.

> > I am not the first one.... See Rik's posts regarding the reasons for his 
> > new page replacement algorithms.
> 
> Different issue, isn't it? Rik wants to be smarter in figuring out which
> pages to throw away. More work per page == worse for you.

Rik is trying to solve the same issue in a different way. He is trying to 
manage gazillion entries better instead of reducing the entries to be 
managed. That can only work in a limited way. Drastic reductions in the 
entries to be manages have good effects in multiple ways. Reduce 
management overhead, improve I/O throughput, etc etc.

-
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/