linux-kernel - Re: xfs: does mkfs.xfs require fancy switches to get decent performance? (was Tux3 Report: How fast can we fsync?)

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Message-ID: <5551FF6F.8060000@symas.com>
Date:	Tue, 12 May 2015 14:26:07 +0100
From:	Howard Chu <hyc@...as.com>
To:	Daniel Phillips <daniel@...nq.net>, Pavel Machek <pavel@....cz>
Cc:	Theodore Ts'o <tytso@....edu>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Dave Chinner <david@...morbit.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tux3@...3.org, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: xfs: does mkfs.xfs require fancy switches to get decent
 performance? (was Tux3 Report: How fast can we fsync?)

Daniel Phillips wrote:
> On 05/12/2015 02:03 AM, Pavel Machek wrote:
>> I'd call system with 65 tasks doing heavy fsync load at the some time
>> "embarrassingly misconfigured" :-). It is nice if your filesystem can
>> stay fast in that case, but...
>
> Well, Tux3 wins the fsync race now whether it is 1 task, 64 tasks or
> 10,000 tasks. At the high end, maybe it is just a curiosity, or maybe
> it tells us something about how Tux3 is will scale on the big machines
> that XFS currently lays claim to. And Java programmers are busy doing
> all kinds of wild and crazy things with lots of tasks. Java almost
> makes them do it. If they need their data durable then they can easily
> create loads like my test case.
>
> Suppose you have a web server meant to serve 10,000 transactions
> simultaneously and it needs to survive crashes without losing client
> state. How will you do it? You could install an expensive, finicky
> database, or you could write some Java code that happens to work well
> because Linux has a scheduler and a filesystem that can handle it.
> Oh wait, we don't have the second one yet, but maybe we soon will.
>
> I will not claim that stupidly fast and scalable fsync is the main
> reason that somebody should want Tux3, however, the lack of a high
> performance fsync was in fact used as a means of spreading FUD about
> Tux3, so I had some fun going way beyond the call of duty to answer
> that. By the way, I am still waiting for the original source of the
> FUD to concede the point politely, but maybe he is waiting for the
> code to land, which it still has not as of today, so I guess that is
> fair. Note that it would have landed quite some time ago if Tux3 was
> already merged.

Well, stupidly fast and scalable fsync sounds wonderful to me; it's the 
primary pain point in LMDB write performance now.

http://symas.com/mdb/ondisk/

I look forward to testing Tux3 when usable code shows up in a public repo.

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/
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