On Wednesday, 2020-08-26 at 11:33:30 +01, Dr. David Alan Gilbert wrote:
> * David Edmondson (d...@dme.org) wrote:
>> On Monday, 2020-08-24 at 17:14:31 +08, Chuan Zheng wrote:
>>
>> > Add RamlockDirtyInfo to store sampled page info of each ramblock.
>> >
>> > Signed-off-by: Chuan Zheng <zhengch...@huawei.com>
>> > ---
>> > migration/dirtyrate.h | 18 ++++++++++++++++++
>> > 1 file changed, 18 insertions(+)
>> >
>> > diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
>> > index 33669b7..70000da 100644
>> > --- a/migration/dirtyrate.h
>> > +++ b/migration/dirtyrate.h
>> > @@ -19,6 +19,11 @@
>> > */
>> > #define DIRTYRATE_DEFAULT_SAMPLE_PAGES 512
>> >
>> > +/*
>> > + * Record ramblock idstr
>> > + */
>> > +#define RAMBLOCK_INFO_MAX_LEN 256
>> > +
>> > /* Take 1s as default for calculation duration */
>> > #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC 1
>> >
>> > @@ -27,6 +32,19 @@ struct DirtyRateConfig {
>> > int64_t sample_period_seconds; /* time duration between two sampling
>> > */
>> > };
>> >
>> > +/*
>> > + * Store dirtypage info for each ramblock.
>> > + */
>> > +struct RamblockDirtyInfo {
>> > + char idstr[RAMBLOCK_INFO_MAX_LEN]; /* idstr for each ramblock */
>> > + uint8_t *ramblock_addr; /* base address of ramblock we measure */
>> > + uint64_t ramblock_pages; /* ramblock size in 4K-page */
>>
>> It's probably a stupid question, but why not store a pointer to the
>> RAMBlock rather than copying some of the details?
>
> I think I figured that out in the last round; this code runs as:
>
> rcu lock {
> calculate initial CRCs
> }
>
> <sleep 1 second ish>
> rcu lock {
> calculate new CRCs
> }
>
> A RAMBlock might get deleted between the two.
Makes sense, thanks.
dme.
--
Why does it have to be like this? I can never tell.
