linux-kernel - Re: [PATCH 0/4] zsmalloc improvements

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Date:	Thu, 12 Jul 2012 06:40:30 -0400
From:	Konrad Rzeszutek Wilk <konrad@...nok.org>
To:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Nitin Gupta <ngupta@...are.org>,
	Minchan Kim <minchan@...nel.org>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] zsmalloc improvements

On Wed, Jul 11, 2012 at 03:48:28PM -0500, Seth Jennings wrote:
> On 07/11/2012 02:42 PM, Konrad Rzeszutek Wilk wrote:
> >>>> Which architecture was this under? It sounds x86-ish? Is this on
> >>>> Westmere and more modern machines? What about Core2 architecture?
> >>>>
> >>>> Oh how did it work on AMD Phenom boxes?
> >>>
> >>> I don't have a Phenom box but I have an Athlon X2 I can try out.
> >>> I'll get this information next Monday.
> >>
> >> Actually, I'm running some production stuff on that box, so
> >> I rather not put testing stuff on it.  Is there any
> >> particular reason that you wanted this information? Do you
> >> have a reason to believe that mapping will be faster than
> >> copy for AMD procs?
> > 
> > Sorry for the late response. Working on some ugly bug that is taking
> > more time than anticipated.
> > My thoughts were that these findings are based on the hardware memory
> > prefetcher. The Intel
> > machines - especially starting with Nehelem have some pretty
> > impressive prefetcher where
> > even doing in a linked list 'prefetch' on the next node is not beneficial.
> > 
> > Perhaps the way to leverage this is to use different modes depending
> > on the bulk of data?
> > When there is a huge amount use the old method, but for small use copy
> > (as it would
> > in theory stay in the cache longer).
> 
> Not sure what you mean by "bulk" or "huge amount" but the
> maximum size of mapped object is PAGE_SIZE and the typical
> size more around PAGE_SIZE/2. So that is what I'm
> considering.  Do you think it makes a difference with copies
> that small?

I was thinking in terms of time. So if there are many requests coming
in at some threshold, then use one method.
> 
> Thanks,
> Seth
> 
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