Re: Fixed at last!

Thanks for the great job! I'll merge changes immediately to give an
opportunity to test them more widely.

01.06.12 14:25, Nigel Cunningham написав(ла):
> Hi all.
> 
> I thought you might like to hear some good news.
> 
> I finally found some time to put a concerted effort into finding and
> fixing the cause of TuxOnIce not working with the BFS scheduler. The
> issue turned out, I think, to be the same one that's been causing those
> pesky occasional failures to read compressed data (the -22 error).
> 
> The problem turned out to be nice and simple: when we create the extra
> threads for doing multithreaded I/O, we bind each one to its own CPU.
> That's find and dandy until we get to the atomic copy, when we do CPU
> hotplugging. The affinities get broken and threads end up stomping over
> each others' memory. It seems that BFS does a better job of breaking the
> affinities than the normal scheduler, which made the problem easier to
> find.
> 
> So, after thinking all this time that it was a locking problem in the
> code that was already there, it turned out to be a few lines of code
> that weren't there instead: the solution is to simply get each thread to
> remember its affinity and reset it before it starts to do any work.
> 
> And the outcome:
> 
> TuxOnIce debugging info:
> - TuxOnIce core  : 3.2.1
> - Kernel Version : 3.2.13+
> - Compiler vers. : 4.7
> - Attempt number : 1
> - Parameters     : 0 667661 0 1 -2 0
> - Overall expected compression percentage: 0.
> - Compressor is 'lzo'.
>   Compressed 1095974912 bytes into 261283523 (76 percent compression).
> - Block I/O active.
> - Max outstanding reads 1866. Max writes 3449.
>   Memory_needed: 1024 x (4096 + 352 + 112) = 4669440 bytes.
>   Free mem throttle point reached 0.
> - Swap Allocator enabled.
>   Swap available for image: 2097151 pages.
> - File Allocator active.
>   Storage available for image: 0 pages.
> - I/O speed: Write 782 MB/s, Read 1061 MB/s.
> - Extra pages    : 74 used/2000.
> - Result         : Succeeded.
> nigel@nigel:~$
> 
> Those astoundingly big speeds are due to this being an Intel 520 SSD on
> a quad-core laptop. I don't usually get a GB/s. More like about 900MB/s.
> This is having just booted - no real apps loaded.
> 
> Patches being applied to git trees now, and will be pushed to github
> shortly. Hopefully I'll also get some patches up on tuxonice.net soon.
> 
> Nigel
> _______________________________________________
> TuxOnIce-devel mailing list
> [email protected]
> http://lists.tuxonice.net/listinfo/tuxonice-devel

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