On Fri, 21 Apr 2000, Kris Kennaway wrote:
> OpenSSL includes asm code for several platforms to speed up various
> operations. Currently we don't build any of this - the attached patch
> turns on asm code for Pentiums and above (it relies on an uncommitted
> patch to sys.mk which defined MACHINE_CPU ?= i386). Set MACHINE_CPU to
> "i586" or "i686" (both are actually identical at present) and rebuild.
On Sat, Apr 22, 2000 at 02:35:51PM +1000, Matthew N. Dodd wrote:
>Can these be turned on at runtime?
Not the way the libraries are currently structured. There are a
number of libraries where we would get significant speedups by
supporting target-dependent code. I can think of three possible
ways of supporting this:
1) Use machine-depend shared libraries to replace functions in the
standard shared libraries. This approach is used on Solaris -
the rtld automatically loads a machine-specific library (if it
exists) before libc.so. The disadvantages are:
- no support for static executables or in-line functions
- slower startup due to the extra libraries (particularly if
Kris's idea of an ordered list of machine architectures)
- increased VM usage due to multiple function versions in
the process address space
- I'm not sure how difficult it would be to integrate into
FreeBSD's lazy binding scheme
2) Use indirect function calls, with run-time initialisation to
setup the pointers. This approach is used in the kernel for
bzero/bcopy. The disadvantages are:
- no support for in-line functions
- need to invoke a library initialisation routine (not too
difficult with ELF)
- increased function call overheads (indirect rather than
direct calls).
- increased VM usage due to multiple function versions in
the process address space
3) Have separate library versions for each target.
- Significant increase in disk space occupied by libraries
All the approaches increase the build time since multiple copies
of functions need to be built.
Peter
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