This is a follow up on the other commit "migration/ram: avoid to do log clear in the last round" but for postcopy.
https://lore.kernel.org/r/20250514115827.3216082-1-yanfei...@bytedance.com I can observe more than 10% reduction of average page fault latency during postcopy phase with this optimization: Before: 268.00us (+-1.87%) After: 232.67us (+-2.01%) The test was done with a 16GB VM with 80 vCPUs, running a workload that busy random writes to 13GB memory. Cc: Yanfei Xu <yanfei...@bytedance.com> Signed-off-by: Peter Xu <pet...@redhat.com> --- migration/ram.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/migration/ram.c b/migration/ram.c index a1d0e8ada2..cd4aafd15c 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -835,8 +835,10 @@ static inline bool migration_bitmap_clear_dirty(RAMState *rs, * protections isn't needed as we know there will be either (1) no * further writes if migration will complete, or (2) migration fails * at last then tracking isn't needed either. + * + * Do the same for postcopy due to the same reason. */ - if (!rs->last_stage) { + if (!rs->last_stage && !migration_in_postcopy()) { /* * Clear dirty bitmap if needed. This _must_ be called before we * send any of the page in the chunk because we need to make sure -- 2.49.0
