linux-kernel - Re: [FYI] tux3: Core changes

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Message-ID: <alpine.DEB.2.02.1507311124390.11360@nftneq.ynat.uz>
Date:	Fri, 31 Jul 2015 11:29:51 -0700 (PDT)
From:	David Lang <david@...g.hm>
To:	Daniel Phillips <daniel@...nq.net>
cc:	Raymond Jennings <shentino@...il.com>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Rik van Riel <riel@...hat.com>, Jan Kara <jack@...e.cz>,
	tux3@...3.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [FYI] tux3: Core changes

On Fri, 31 Jul 2015, Daniel Phillips wrote:

> Subject: Re: [FYI] tux3: Core changes
> 
> On Friday, July 31, 2015 8:37:35 AM PDT, Raymond Jennings wrote:
>> Returning ENOSPC when you have free space you can't yet prove is safer than
>> not returning it and risking a data loss when you get hit by a write/commit
>> storm. :)
>
> Remember when delayed allocation was scary and unproven, because proving
> that ENOSPC will always be returned when needed is extremely difficult?
> But the performance advantage was compelling, so we just worked at it
> until it worked. There were times when it didn't work properly, but the
> code was in the tree so it got fixed.
>
> It's like that now with page forking - a new technique with compelling
> advantages, and some challenges. In the past, we (the Linux community)
> would rise to the challenge and err on the side of pushing optimizations
> in early. That was our mojo, and that is how Linux became the dominant
> operating system it is today. Do we, the Linux community, still have that
> mojo?

We, the Linux Community have less tolerance for losing people's data and 
preventing them from operating than we used to when it was all tinkerer's 
personal data and secondary systems.

So rather than pushing optimizations out to everyone and seeing what breaks, we 
now do more testing and checking for failures before pushing things out.

This means that when something new is introduced, we default to the safe, 
slightly slower way initially (there will be enough other bugs to deal with in 
any case), and then as we gain experience from the tinkerers enabling the 
performance optimizations, we make those optimizations reliable and only then 
push them out to all users.

If you define this as "loosing our mojo", then yes we have. But most people see 
the pace of development as still being high, just with more testing and 
polishing before it gets out to users.

David Lang
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