guest-diag: single-instance scanner start + full-re-assert backoff

r148 ran THREE guest scanners (pin_gr_stream install_and_start retried
while a partially-failed first attempt had already started one, and the
pid-file kill missed it). Each scanner re-asserted the whole CE pair set
every 2 s; with a fully fragmented pair set (descending PAs, one page per
line) that is ~2 k debugfs writes/s per scanner, and the guest hit load 19
with clients wedged spinning in userspace.

- pin_gr_stream._start_cmd: kill EVERY existing scanner first (pattern
  assembled at runtime with printf so the command's own cmdline cannot
  self-match), then start exactly one.
- guest_pin_stream._emit_ce_mem_delta: the full re-assert keeps its 1.5 s
  cadence for the first STREAM_FULLREM_FAST_S seconds of a mem's life (the
  client-switch flush race), then backs off to STREAM_FULLREM_SLOW_S (10 s)
  as a safety net. Configurable via env.

0 files changed, 0 insertions, 0 deletions