Messages in this thread | | | Date | Thu, 2 Apr 2009 20:05:40 -0600 | Subject | Re: EXT4-ish "fixes" in UBIFS | From | "Trenton D. Adams" <> |
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On Thu, Apr 2, 2009 at 7:55 PM, David Rees <drees76@gmail.com> wrote: > On Thu, Apr 2, 2009 at 5:28 PM, Trenton D. Adams > <trenton.d.adams@gmail.com> wrote: >> On Thu, Apr 2, 2009 at 6:24 PM, Trenton D. Adams >> <trenton.d.adams@gmail.com> wrote: >>> Yes, mounting "-o sync" does improve ext3 performance. It sucks >>> though, because I do want quick writes. And mounting with sync option >>> slows down to disk io speeds. In my case, that's between 20 and 23 >>> megabytes per second *big frown, quivering lip, and tears in my eyes*. >>> :P >>> >> >> Oh, I should have clarified. It improves performance under heavy >> load. Under normal load, mounting without sync is fine. What I tend >> to do is mount with "remount,rw,sync" when heavy load is starting. >> Then my system goes slowly, but latency is good. Then, when it's all >> done (say a big compile, or job, or whatever), I remount without sync >> again. >> >> I'm thinking of writing a script that monitors performance, and >> remounts as needed, lol. WHAT A HACK. hehe. > > All you're doing here is implementing the lowering of dirty data > limits in the VM dynamically based on how long fsyncs take. > > Linus outlined this specific strategy as "the ideal siutation" > somewhere in the depths of "That filesystem thread".
I thought he said it was a HORRIBLE solution. :D I recall him slamming Andrew over it. Unless you're referring to the kernel actually doing it on the fly.
> > Look at the new in 2.6.29 dirty*bytes parameters in > Documentation/sysctl/vm.txt for more info. By lowering those values, > you can effectively turn normal writes into synchronous writes which > will greatly reduce latency of fsync under heavy write load. > > In previous kernels you can tweak dirty_ratio and > dirty_background_ratio, but they don't have the granularity of the new > knobs. Although if you are talking about just remounting in sync > mode, they may work for you at least as a proof of concept. ;-) > > -Dave >
dirty_ratio and dirty_background never really had any affect for me. I'll look into the other parameters. Waiting for the checkout again, as I am currently under a heavy rsync load (*rolls eyes*).
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