diff options
| author | Peter Xu <peterx@redhat.com> | 2025-06-13 10:08:01 -0400 |
|---|---|---|
| committer | Fabiano Rosas <farosas@suse.de> | 2025-07-11 10:37:37 -0300 |
| commit | adb13d6e42d6e0084e19a41303138d5d022e5904 (patch) | |
| tree | 3df2d37b8c106dc7d33b30a68c6802d0f6591869 | |
| parent | 7aaa1fc072ca7b9abf08c62504faa96126b583ce (diff) | |
| download | qemu-adb13d6e42d6e0084e19a41303138d5d022e5904.zip qemu-adb13d6e42d6e0084e19a41303138d5d022e5904.tar.gz qemu-adb13d6e42d6e0084e19a41303138d5d022e5904.tar.bz2 | |
migration/postcopy: Avoid clearing dirty bitmap for postcopy too
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.xu@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.xu@bytedance.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250613140801.474264-12-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
| -rw-r--r-- | migration/ram.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/migration/ram.c b/migration/ram.c index e4871b4..7208bc1 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 |