linux-kernel - Re: Tux3 Report: How fast can we fsync?

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Date:	Thu, 30 Apr 2015 05:50:57 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Daniel Phillips <daniel@...nq.net>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tux3@...3.org, Theodore Ts'o <tytso@....edu>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: Tux3 Report: How fast can we fsync?

On Wed, 2015-04-29 at 13:40 -0700, Daniel Phillips wrote:
> On Wednesday, April 29, 2015 9:42:43 AM PDT, Mike Galbraith wrote:
> >
> > [dbench bakeoff]
> >
> > With dbench v4.00, tux3 seems to be king of the max_latency hill, but
> > btrfs took throughput on my box.  With v3.04, tux3 took 1st place at
> > splashing about in pagecache, but last place at dbench -S.
> >
> > Hohum, curiosity satisfied.
> 
> Hi Mike,
> 
> Thanks for that. Please keep in mind, that was our B team, it does a
> full fs sync for every fsync. Maybe a rematch when the shiny new one
> lands? Also, hardware? It looks like a single 7200 RPM disk, but it
> would be nice to know. And it seems, not all dbench 4.0 are equal.
> Mine doesn't have a -B option.

Hm, mine came from git://git.samba.org/sahlberg/dbench.git.  The thing
has all kinds of cool options I have no clue how to use.

Yeah, the box is a modern plane jane, loads of CPU, cheap a$$ spinning
rust IO.  It has an SSD, but that's currently occupied by games OS.
I'll eventually either buy a bigger one or steal it from winders.  The
only thing stopping me is my inherent mistrust of storage media that has
no moving parts, but wears out anyway, and with no bearings whining to
warn you :)

> That order of magnitude latency difference is striking. It sounds
> good, but what does it mean? I see a smaller difference here, maybe
> because of running under KVM.

That max_latency thing is flush.

	-Mike

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