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    SubjectRe: ima: use of radix tree cache indexing == massive waste of memory?
    On 10/16/2010 07:11 PM, Dave Chinner wrote:
    > On Sat, Oct 16, 2010 at 05:54:11PM -0700, J.H. wrote:
    >> There does seem to be a boot option to disable it, but it seems to be on
    >> by default if it's compiled in, and it's not like it's obvious that this
    >> is there and chewing up resources, is there a way to find out how much
    >> memory this is chewing up?
    >
    > $ grep iint_cache /proc/slabinfo | awk '// { print $2 * ($4 + 560) / 1048576 "MiB" }'
    > 1164.91MiB
    > $

    Exciting, I saw that too. Not sure I'm going to get to do a reboot on
    master before Kernel summit (and it's OS upgrade) but I'm re-compiling
    the kernel with IMA disabled.

    Master's live backup machine was chewing nearly 4G of memory, and
    if/when I flip some of the big frontend machines over this is going to
    be a completely unacceptable waste of memory.

    For the record I'm really not happy or keen on having to maintain a
    custom kernel just to get this disabled, but if it's going to save me 4G
    on a single quiet machine I can only assumes it's going to save me
    several 10s of gigs on some of the bigger machines.

    > $ while [ 1 ]; do
    >> grep iint_cache /proc/slabinfo | awk '// { print $2 * ($4 + 560) / 1048576 "MiB" }'
    >> sleep 5
    >> done
    > 955.706MiB
    > 937.438MiB
    > 928.851MiB
    > 920.912MiB
    > 919.067MiB
    > 919.086MiB
    > 919.111MiB
    > .....
    >
    > This is only with about 1.2M inodes cached - yesterday I saw the
    > inode cache grow to 3.5M inodes during an rsync run....
    >
    > Also, it's doing a good job of fragmenting the radix tree node cache
    > - it's currently at 50% population - 3.8M entries, 1.9M in use. i.e.
    > wasting another ~1GB of RAM itself right now....

    Ouch, thanks for giving us a heads up on it, definately not something I
    expected to quietly creep in and bite me. I should have a solution, if
    one I'm not happy with, in the short term. Hopefully Fedora/upstream
    will have a better solution soon.

    For the record I liked the explicit opt-in that was mentioned vs. and
    automatic opt-in without disable we have now.

    - John 'Warthog9' Hawley


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