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The Performance Of EXT4 Then & Now

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  • fxfuji
    replied
    Methodology ?

    Something is rather odd about the 2 GB IOZone results... for the latest kernels, the write throughput is nearly 2x the read throughput?

    In what world do you live in that hard disks can write data so much faster than they can read it? I'm wondering if there's something wrong with the methodology or measurement, perhaps related to ext4 supporting delayed writes?

    I think it's important not just to do and publish benchmark results, but also to investigate and understand when the results don't pass the 'common-sense test.' Otherwise, the benchmark numbers are no more useful than a random set of digits.

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  • Apopas
    replied
    Done! It is bug 223638.
    I'm posting it here in case someone else cares for it as well...

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  • deanjo
    replied
    Originally posted by Apopas View Post
    With XFS at least, seems to be normal.
    If I submit it as a bug to KDE, are you gonna to confirm it?
    Sure I will, just pm me the link to it.

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  • Apopas
    replied
    With XFS at least, seems to be normal.
    If I submit it as a bug to KDE, are you gonna to confirm it?

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  • deanjo
    replied
    Originally posted by Apopas View Post
    Hmmm any possibility to be KDE's bug?
    I would almost lean towards that as to who's bug it is. I don't think I've ever truthfully seen a true accurate progress meter though on high speed transfers on any OS or desktop though.

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  • Apopas
    replied
    Hmmm any possibility to be KDE's bug?

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  • deanjo
    replied
    Originally posted by Apopas View Post
    So I suppose there is not practical reason for such behaviour and since other filesystems acts correctly, I guess it's a minor bug that should be fixed, right?
    I suppose, I just learned to live with it as one of those things you get used too since the true actual writing performance doesn't seem to suffer.

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  • Apopas
    replied
    So I suppose there is not practical reason for such behaviour and since other filesystems acts correctly, I guess it's a minor bug that should be fixed, right?

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  • deanjo
    replied
    Originally posted by Apopas View Post
    I see. That means if for some reason RAM is full or there is not enough of it, it delays the copy?
    No it seems more like the initial speed reported is actually dumping to ram then once that is full and the transfer is slower the "meter" then over compensates and reduces the reported speed. Maybe doing it over a network just exaggerates the result even more as initial speeds are well above network capacity.

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  • Apopas
    replied
    Originally posted by deanjo View Post
    I've noticed this too, it seems to behave the same as copying from the local machine to a remote machine. (Buffering to ram maybe?) On a network situation copying from a remote machine to the local displays accurate speeds.
    I see. That means if for some reason RAM is full or there is not enough of it, it delays the copy?
    Last edited by Apopas; 01-20-2010, 05:39 PM.

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