Messages in this thread | | | Date | Thu, 15 Nov 2007 16:41:16 -0800 | From | "H. Peter Anvin" <> | Subject | Re: Why preallocate pmd in x86 32-bit PAE? |
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William Lee Irwin III wrote: > > There may be bigger fish to fry in terms of per-process overhead, if > you're trying to cut that down. The trouble with trying to address > some of those is that there is mutual antagonism between compactness > and expansibility in the process address space layout, so you'll end > up instantiating a lot more than you want barring some sort of provision > for a compact address space layout. Pagetable sharing is a far more > powerful resource scalability method, though it also needs cooperation > in user address space layout to reap its gains. > > There are other overheads, of course, though they're more typically > per-something besides processes. >
I think Jeremy's question was due to trying to reduce the 32/64-bit differences. Performance-wise, it might add a small amount to user setup time (a typical 32-bit process will need all four, for the main binary, libraries, stack and kernel, respectively) but it is probably not significant (although I'd like to see numbers just in case).
-hpa
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