Re: [PATCH v1 1/5] kvm,memory: Optimize dirty page collection for dirty ring

[Hyman Huang]

在 2022/3/23 11:18, wucy11@chinatelecom.cn 写道:
> From: Chongyun Wu <wucy11@chinatelecom.cn>
>
> When log_sync_global of dirty ring is called, it will collect
> dirty pages on all cpus, including all dirty pages on memslot,
> so when memory_region_sync_dirty_bitmap collects dirty pages
> from KVM, this interface needs to be called once, instead of
> traversing every dirty page. Each memslot is called once,
> which is meaningless and time-consuming. So only need to call
> log_sync_global once in memory_region_sync_dirty_bitmap.
>
> Signed-off-by: Chongyun Wu <wucy11@chinatelecom.cn>
> ---
>   softmmu/memory.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/softmmu/memory.c b/softmmu/memory.c
> index 8060c6d..46c3ff9 100644
> --- a/softmmu/memory.c
> +++ b/softmmu/memory.c
> @@ -2184,6 +2184,12 @@ static void memory_region_sync_dirty_bitmap(MemoryRegion 
> *mr)
>                */
>               listener->log_sync_global(listener);
>               trace_memory_region_sync_dirty(mr ? mr->name : "(all)", 
> listener->name, 1);
> +            /*
> +             * The log_sync_global of the dirty ring will collect the dirty
> +             * pages of all memslots at one time, so there is no need to
> +             * call log_sync_global once when traversing each memslot.
> +             */
> +            break;
To the code logic itself, if a listener does not implement the 
log_sync_global callback, it never go there. If not, it should not break 
because we never know which callback is what dirty ring want.
IMHO, maybe the modification should remove from the common logic and 
implemented somewhere else, i havn't think it through yet.
>           }
>       }
>   }

--
Best regard

Hyman Huang(黄勇)