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    SubjectRe: [RFC] extents support for EXT3
    Alex Tomas wrote:
    >>>>>>Ed Sweetman (ES) writes:
    > ES> I was testing this with only a single partition mounted with extents
    > ES> enabled when benchmarking. Ext3 gave no messages of being mounted
    > ES> afterbootup with or without extents so to make sure i had extents
    > ES> enabled i booted with all my partitions with the extents option. I
    > ES> suspect then my problems began. I'm completely unaware of the extent
    > ES> of the damage enabling extents has done since most of the important
    > ES> things were opened, not created during my extents use. In any case it
    > ES> may be that the reason why init is not able to be found is because i
    > ES> used apt and upgraded my system ...and I dont remember if i had
    > ES> extents enabled at the time or not. If my init is in extents format
    > ES> though, then why is a patched kernel able to read it with extents not
    > ES> being enabled via the omunt option where as kernels without the patch
    > ES> cannot. Is extents able to be read from a fs even when it's not
    > ES> mounted with the option but not written? I'm kinda confused, this
    > ES> aspect of extents wasn't in the original email.
    > well, on my testbox I use _patched with extents_ ext3 as / and /boot partitions.
    > I haven't seen any problems on them. with patch, ext3 look at special EXTENTS
    > flag in inode (this flag is set up only for newly created files on fs being
    > mounted with extents enabled) and calls apropriate routines. thus, it will
    > call extents routines for those file even if fs is being mounted with extents
    > disabled. I really do believe that your root filesystem haven't been mounted
    > with extents enabled, so init must be stored in good old format.

    Ok well little wait on the non-patched bootup.

    I booted with test4-mm2 patched

    Throughput 221.812 MB/sec 16 procs ext2
    Throughput 159.495 MB/sec 16 procs ext3-extents (definitely enabled)
    Throughput 147.598 MB/sec 16 procs ext3 (patched but disabled)

    There is an obvious improvement, but nothing near the 70+% increase you
    saw. Subsequent runs run anything from a little lower than above for
    extents to 167MB/s.

    I'm using the largest inode size possible for ext3 for the filesystem

    By the way, what's the behavior of opening an existing non-extent file
    and writing and reading to it while the partition is mounted with
    extents enabled?

    > ES> i'm going to try and boot a kernel without the extents patch (so far
    > ES> hasn't been possible) and run dbench again and see if i get different
    > ES> numbers. I'm almost suspecting extents being enabled no matter what i
    > ES> mount the fs's as.
    > that would be fine!

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