[Lldb-commits] [PATCH] [NativeProcessLinux] Use fast memory reads, if the system supports it

[Pavel Labath]

Hi ovyalov, vharron,

Memory reads using the ptrace API need to be executed on a designated thread
and in 4-byte increments. The process_vm_read syscall has no such requirements
and it is about 50 times faster. This patch makes lldb-server use the faster
API if the target kernel supports it. Kernel support for this feature is
determined at runtime. Using process_vm_writev in the same manner is more
complicated since this syscall (unlike ptrace) respects page protection settings
and so it cannot be used to set a breakpoint, since code pages are typically
read-only. However, memory writes are not currently a performance bottleneck as
they happen much more rarely.

http://reviews.llvm.org/D10488

Files:
  include/lldb/Host/linux/Uio.h
  source/Host/android/LibcGlue.cpp
  source/Plugins/Process/Linux/NativeProcessLinux.cpp

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