Messages in this thread | | | From | "Hua Zhong" <> | Subject | RE: [PATCH 0/8][RFC] IO latency/throughput fixes | Date | Mon, 6 Apr 2009 22:23:31 -0700 |
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The (small) set of people that rely on "ordered" understand the problem, as long as they are aware of the change (no, I don't think reading through all changelogs from their old kernel to the new one is a realistic option).
So a config option should be good enough to get them to notice the change (I assume a missing default will force them to choose an option), and therefore explicitly add the -o ordered option to their scripts.
On the other hand a run-time tunable has no real point.
> -----Original Message----- > From: Linus Torvalds [mailto:torvalds@linux-foundation.org] > Sent: Monday, April 06, 2009 10:02 PM > To: Trenton D. Adams > Cc: Chris Mason; Theodore Tso; Hua Zhong; Jens Axboe; Linux Kernel > Mailing List > Subject: Re: [PATCH 0/8][RFC] IO latency/throughput fixes > > > > On Mon, 6 Apr 2009, Trenton D. Adams wrote: > > > > What about a procfs setting instead? Is there a policy about why > > something should be in procfs or /sys, or as a kernel config option? > > That's basically as small as the patch you just made, right? > > I'm never really against making things dynamically tunable, but this > already was, and that wasn't really the issue. > > Sure, you can just re-mount your filesystem with different options. > That's > what I did while testing - my /home is on a drive of its own, so I > would > just log out and as root unmount and re-mount with > data=ordered/writeback, > and log in and test again. > > So dynamic tuning is good. But at the same time, having a tuning option > is > _never_ an excuse for not getting the default right in the first place. > It's just a cop-out to say "hey, the default may be wrong for you, but > you > can always tune it locally with XYZ". > > The thing is, almost nobody does that. Partly because it needs effort > and > knowledge, partly because after a few years the number of tuning knobs > are > in the hundreds for every little thing. > > So instead, leave the tuning for the _really_ odd cases (if you use > your > machine as an IP router, you hopefully know enough to tune it if you > really care). Not for random general-purpose "use for whatever" kind of > thing. > > > I'm just thinking that something like this, where people want one > > thing or the other, but may not know it when they install Linux, > might > > like to change it realtime. Especially if they are a Linux newbie, > > and don't know how to compile their own kernel. Or don't have time > to > > maintain their own kernel installs. > > Oh absolutely. I'm not expecting people to compile their own kernels. > I'm > expecting that within a few months, most modern distributions will have > (almost by mistake) gotten a new set of saner defaults, and anybody who > keeps their machine up-to-date will see a smoother experience without > ever > even realizing _why_. > > Linus
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