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Re: [Qemu-devel] [PATCH 2/2] migration/xbzrle: cleanup the handling cach
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] migration/xbzrle: cleanup the handling cache miss condition |
Date: |
Fri, 7 Jun 2019 20:01:14 +0100 |
User-agent: |
Mutt/1.11.4 (2019-03-13) |
* Wei Yang (address@hidden) wrote:
> For cache miss condition not in last_stage, we need to insert data into
> cache. When this step succeed, current_data should be updated. While no
> matter these checks pass or not, -1 is returned.
>
> Based on this, the logic in cache miss handling could be simplified a
> little.
>
> Signed-off-by: Wei Yang <address@hidden>
> ---
> migration/ram.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 878cd8de7a..67ba075cc4 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1572,15 +1572,14 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> if (!cache_is_cached(XBZRLE.cache, current_addr,
> ram_counters.dirty_sync_count)) {
> xbzrle_counters.cache_miss++;
> - if (!last_stage) {
> - if (cache_insert(XBZRLE.cache, current_addr, *current_data,
> - ram_counters.dirty_sync_count) == -1) {
> - return -1;
> - } else {
> - /* update *current_data when the page has been
> - inserted into cache */
> - *current_data = get_cached_data(XBZRLE.cache, current_addr);
> - }
> + if (!last_stage &&
> + !cache_insert(XBZRLE.cache, current_addr, *current_data,
> + ram_counters.dirty_sync_count)) {
> + /*
> + * update *current_data when the page has been inserted into
> + * cache
> + */
> + *current_data = get_cached_data(XBZRLE.cache, current_addr);
No this change doesn't gain anything and I find the original easier to
read.
This function is really subtle, every time I do anything with it I have
to think really hard about it, so ease of reading is more important.
Dave
> }
> return -1;
> }
> --
> 2.19.1
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK