* [Patch v2] Don't sync volatile memory
@ 2025-06-16 20:56 Chaney, Ben
2025-06-16 21:18 ` Peter Xu
0 siblings, 1 reply; 2+ messages in thread
From: Chaney, Ben @ 2025-06-16 20:56 UTC (permalink / raw)
To: Peter Xu
Cc: David Hildenbrand, Michael S. Tsirkin, yury-kotov@yandex-team.ru,
dgilbert@redhat.com, beata.michalska@linaro.org,
richard.henderson@linaro.org, alex.bennee@linaro.org,
peter.maydell@linaro.org, junyan.he@intel.com,
imammedo@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com,
philmd@linaro.org, xiaoguangrong.eric@gmail.com, Tottenham, Max,
Hunt, Joshua, Glasgall, Anna, qemu-stable@nongnu.org
Not all pmem regions are backed by non-volatile memory. Syncing volatile
memory provides no benefit, but can cause performance issues is some
cases. Only sync memory that is marked as non-volatile.
Signed-off-by: Ben Chaney <bchaney@akamai.com>
Fixes: bd108a44bc29 (migration: ram: Switch to ram block writeback)
---
migration/ram.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/migration/ram.c b/migration/ram.c
index d26dbd37c4..e857b579d6 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3672,7 +3672,9 @@ static int ram_load_cleanup(void *opaque)
RAMBlock *rb;
RAMBLOCK_FOREACH_NOT_IGNORED(rb) {
- qemu_ram_block_writeback(rb);
+ if (memory_region_is_nonvolatile(rb->mr)) {
+ qemu_ram_block_writeback(rb);
+ }
}
xbzrle_load_cleanup();
--
2.40.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Patch v2] Don't sync volatile memory
2025-06-16 20:56 [Patch v2] Don't sync volatile memory Chaney, Ben
@ 2025-06-16 21:18 ` Peter Xu
0 siblings, 0 replies; 2+ messages in thread
From: Peter Xu @ 2025-06-16 21:18 UTC (permalink / raw)
To: Chaney, Ben
Cc: David Hildenbrand, Michael S. Tsirkin, yury-kotov@yandex-team.ru,
dgilbert@redhat.com, beata.michalska@linaro.org,
richard.henderson@linaro.org, alex.bennee@linaro.org,
peter.maydell@linaro.org, junyan.he@intel.com,
imammedo@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com,
philmd@linaro.org, xiaoguangrong.eric@gmail.com, Tottenham, Max,
Hunt, Joshua, Glasgall, Anna, qemu-stable@nongnu.org
On Mon, Jun 16, 2025 at 08:56:50PM +0000, Chaney, Ben wrote:
> Not all pmem regions are backed by non-volatile memory. Syncing volatile
> memory provides no benefit, but can cause performance issues is some
> cases. Only sync memory that is marked as non-volatile.
>
> Signed-off-by: Ben Chaney <bchaney@akamai.com>
> Fixes: bd108a44bc29 (migration: ram: Switch to ram block writeback)
I've queued it with an update on the subject and commit message, as
following:
migration: Don't sync volatile memory after migration completes
Syncing volatile memory provides no benefit, instead it can cause
performance issues in some cases. Only sync memory that is marked as
non-volatile after migration completes on destination.
Thanks,
> ---
> migration/ram.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index d26dbd37c4..e857b579d6 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3672,7 +3672,9 @@ static int ram_load_cleanup(void *opaque)
> RAMBlock *rb;
>
> RAMBLOCK_FOREACH_NOT_IGNORED(rb) {
> - qemu_ram_block_writeback(rb);
> + if (memory_region_is_nonvolatile(rb->mr)) {
> + qemu_ram_block_writeback(rb);
> + }
> }
>
> xbzrle_load_cleanup();
> --
> 2.40.1
>
--
Peter Xu
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