On 2025-08-28 05:17, Jan Beulich wrote:
The present copy_page_sse2() is useful in case the destination page isn't going to get touched again soon, or if we want to limit churn on the caches. Just rename it, to fit the corresponding {clear,scrub}_page_*() naming scheme.For cases where latency is the most important aspect, or when it is expected that sufficiently large parts of a destination page will get accessed again soon after the copying, introduce a "hot" alternative. Again use alternatives patching to select between a "legacy" and an ERMS variant. Don't switch any callers just yet - this will be the subject of subsequent changes. Signed-off-by: Jan Beulich <jbeul...@suse.com>
Reviewed-by: Jason Andryuk <jason.andr...@amd.com>
--- Of course both pages can be independently hot/cold, and hence more flavors may be necessary here. To avoid the NOP padding (also in clear_page_hot()) we could use a double REP prefix in the replacement code (accounting for the REX one in the code being replaced).
Did my tool chain do it automatically? 0000000000000000 <.altinstr_replacement>: 0: b9 00 10 00 00 mov $0x1000,%ecx 5: f3 f3 a4 repz rep movsb %ds:(%rsi),%es:(%rdi) Regards, Jason
