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]

Date:	Thu, 1 Mar 2007 22:19:48 -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:

> > >From the I/O controller and from the application. 
> 
> Why doesn't the application need to deal with TLB entries?

Because it may only operate on a small section of the file and hopefully 
splice the rest through? But yes support for mmapped I/O would be 
necessary.

> > This would only be a temporary fix pushing the limits to the double or so?
> 
> And using slightly larger page sizes isn't?

There was no talk about slightly. 1G page size would actually be quite 
convenient for some applications.

> > Amortized? The controller still would have to hunt down the 4kb page 
> > pieces that we have to feed him right now. Result: Huge scatter gather 
> > lists that may themselves create issues with higher page order.
> 
> What sort of numbers do you have for these controllers that aren't
> very good at doing sg?

Writing a terabyte of memory to disk with handling 256 billion page 
structs? In case of a system with 1 petabyte of memory this may be rather 
typical and necessary for the application to be able to save its state
on disk.

> Isn't the issue was something like your IO controllers have only a
> limited number of sg entries, which is fine with 16K pages, but with
> 4K pages that doesn't give enough data to cover your RAID stripe?
> 
> We're never going to do a variable sized pagecache just because of that.

No, we need support for larger page sizes than 16k. 16k has not been fine 
for a couple of years. We only agreed to 16k because that was the common 
consensus. Best performance was always at 64k 4 years ago (but then we 
have no numbers for higher page sizes yet). Now we would prefer much 
larger sizes.
-
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/