|To:||Robin Humble <rjh@xxxxxxxxxxxxxxxx>|
|Subject:||Re: fc3 and stacks|
|From:||Eric Sandeen <sandeen@xxxxxxx>|
|Date:||Mon, 14 Mar 2005 14:46:28 -0600|
|References:||<20050310232036.GA19295@lemming.cita.utoronto.ca> <4234E903.email@example.com> <4235D44F.firstname.lastname@example.org> <20050314190915.GB9784@lemming.cita.utoronto.ca>|
|User-agent:||Mozilla Thunderbird 1.0 (X11/20041206)|
Robin Humble wrote:
Some ways forward: - convince RedHat to put 8k stacks (or at least the option for it) and XFS into AS4.
FWIW, I try to steer the conversation away from "xfs is broken with 4k stacks" and towards "4k stacks don't work for some applications." :)
XFS can chew through stack a bit faster than some of the filesystems, to be sure. But I've always meant to try to put together some diabolical "supported" config on RHEL4 and file a bug - say nfs over deeply nested volume managers, or something like that.
- try to make XFS play nicer with 4k stacks - run fc3. fc3 and AS4 are very similar (~ 50% of userland rpms are identical, the rest seem to be fairly minor variations), so if your vendor supports AS4 then it'll almost certainly run fine on fc3
- install AS4 but run a fc3 (recompiled for 8k stacks) kernel
- install AS4 but run a stock kernel.org (or XFS cvs) kernel
Seems like with RHEL3, stock kernel.org kernels don't play nicely. I hope this isn't the case with RHEL4, but I have not tested it.
But rebuilding the stock RHEL4 kernel, with tweaks to turn xfs back on, maybe update xfs, and re-enable 8k stacks should be possible, if not supported by RH. :) Or as suggested by Andi, just pick one of the arches that have larger stack space (x86_64) (hm, I should verify that that's still fine on RH kernels... maybe they made them 1k stacks) :)
The first 2 of these are hard, the last 2 are pretty easy but may not help you from a vendor support point of view. We'll probably choose the last option. The middle option (fc3) is what you are doing now, so you can get some idea of XFS stability with 4k stacks for your particular workload.
I think there are some applications (java?) that can benefit from smaller stacks in terms of overal thread count & memory usage... but I don't know why they went so far as to actually remove the option.
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