linux-kernel - Re: [RESEND] IOZone with transparent huge page cache

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Date:	Tue, 16 Apr 2013 08:57:21 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave Hansen <dave@...1.net>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RESEND] IOZone with transparent huge page cache

Dave Hansen wrote:
> On 04/15/2013 11:17 AM, Kirill A. Shutemov wrote:
> > I run iozone using mmap files (-B) with different number of threads.
> > The test machine is 4s Westmere - 4x10 cores + HT.
> 
> How did you run this, exactly?  Which iozone arguments?

iozone -B -s 21822226/$threads -t $threads -r 4 -i 0 -i 1 -i 2 -i 3

It's slightly modified iozone test from mmtests.

> It was run on ramfs, since that's the only thing that transparent huge page
> cache supports right now?

Correct.

> > ** Initial writers **
> > threads:	        1        2        4        8       16       32       64      128      256
> > baseline:	  1103360   912585   500065   260503   128918    62039    34799    18718     9376
> > patched:	  2127476  2155029  2345079  1942158  1127109   571899   127090    52939    25950
> > speed-up(times):     1.93     2.36     4.69     7.46     8.74     9.22     3.65     2.83     2.77
> 
> I'm a _bit_ surprised that iozone scales _that_ badly especially while
> threads<nr_cpus.  Is this normal for iozone?  What are the units and
> metric there, btw?

The units is KB/sec per process (I used 'Avg throughput per process' from
iozone report). So it scales not that badly.
I will use total children throughput next time to avoid confusion.

> > Minimal speed up is in 1-thread reverse readers - 23%.
> > Maximal is 9.2 times in 32-thread initial writers. It's probably due
> > batched radix tree insert - we insert 512 pages a time. It reduces
> > mapping->tree_lock contention.
> 
> It might actually be interesting to see this at 10, 20, 40, 80, etc...
> since that'll actually match iozone threads to CPU cores on your
> particular system.

Okay.

-- 
 Kirill A. Shutemov
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