On Thu, 2015-03-26 at 08:57 +0000, Richard W.M. Jones wrote: > Is pthread_create used even for the main thread in the process (I > thought the kernel created that). In any case threads aren't being > used explicitly by this process. > > Anyway I guess the guard page is just a hole that causes the process > to abort (as observed) and is not a mechanism for automatically > growing the stack.
Right, It's a mechanism for catching stack overflow reliably, rather than letting it cause random memory corruption. But for the original stack created by the kernel when the process is created, I think you just don't have the guard page. All that stops you is the ulimit. So... we could potentially look for ways to reduce the stack usage of OCaml-compiled code, or you get to keep increasing the limit. It might be worth taking a look at the stack frames and seeing if I did anything entirely stupid when setting them up, and whether they can be made smaller. Although if you said it was averaging ~168 bytes, that doesn't seem *particularly* excessive. Can you see how big the stack actually does get in your worst case, and how much we'd have to shrink by in order to get away without tweaking the ulimit? Perhaps we could also look at using a smaller stack frame between OCaml functions. If we're never using certain registers in the OCaml code generator, we don't need to save them or leave space for them on the stack. All we need to do it ensure that if we're calling out to a C function, we *do* leave enough space in the stack frame for callee- saved registers, right? I concede to being a bit rusty here... :) -- dwmw2
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