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On Sunday 08 May 2005 21:47, Miguel Filipe wrote: |
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> Are there any numbers (benchmarks) about the performance penalty of |
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> pageexec and/or segmexec on intel x86 machines? |
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> |
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> The idea that I have is that page-exec on x86 involves a page-fault |
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> for every (execute) access to a new page that will be treated by |
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> pax... and that is performance-wise .. bad.. |
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It's a page-fault for every access, whether it is write, read or execute. |
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Access type is verified later. Am I right? |
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> And that segmexec is a diferent approach that involves, mirroring the |
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> process address space on two segments with diferent "write" |
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> permissions, and compairing those two, to check if there was any |
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> overwrite of the code segment. |
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> This would mean doubling the mem-usage, at least for the code-segment |
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> in segmexec mode. |
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> |
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> I have the idea that segmexec is advised for being faster (on x86), |
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> but I don't have any numbers, and I was trying to understand the |
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> performance-wise consequences of each implementation. |
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Someone told me the same thing :-p |
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> And in arches that suport no-exec pages (has sparc or amd64), what are |
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> the performance penalties? Anyone can give me some pointers? |
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Using PAGEEXEC, supposedly none. right? |
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> stuff like: kernel compiles, mysql benches, or... any other benchmark |
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> is good for me.. just to "grasp" a idea... |
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On a simple SMP pentium III I can make such benchmarks :-) |
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regards, |
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pedro venda. |
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-- |
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|
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Pedro João Lopes Venda |
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email: pjvenda < at > arrakis.dhis.org |
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http://arrakis.dhis.org |
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