On 02/24/2015 02:50 PM, Maciej W. Rozycki wrote:
On Tue, 24 Feb 2015, Leonid Yegoshin wrote:
For simplicity perhaps on SMP we should just always use hit operations
regardless of the size requested.
High performance folks may not like doing a lot of stuff for 8MB VMA release
instead of flushing 64KB.
What kind of a use case is that, what does it do?
Especially taking into account TLB exceptions and postprocessing in
fixup_exception() for swapped-out/not-yet-loaded-ELF blocks.
The normal use for cacheflush(2) I know of is for self-modifying or other
run-time-generated code, to synchronise caches after a block of machine
code has been patched in -- SYNCI can also be used for that purpose these
days,
SYNCI is only useful in non-SMP kernels.
If a thread is migrated to a different CPU between the SYNCI, and the
attempt to execute the freshly generated code, the new CPU can still
have a dirty ICACHE. So for Linux userspace, cacheflush(2) is your only
option.
David Daney
