[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v4 08/10] migration: fix calculating xbzrle_coun
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH v4 08/10] migration: fix calculating xbzrle_counters.cache_miss_rate |
Date: |
Wed, 22 Aug 2018 12:58:49 +0800 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
On Tue, Aug 21, 2018 at 04:10:27PM +0800, address@hidden wrote:
> From: Xiao Guangrong <address@hidden>
>
> As Peter pointed out:
> | - xbzrle_counters.cache_miss is done in save_xbzrle_page(), so it's
> | per-guest-page granularity
> |
> | - RAMState.iterations is done for each ram_find_and_save_block(), so
> | it's per-host-page granularity
> |
> | An example is that when we migrate a 2M huge page in the guest, we
> | will only increase the RAMState.iterations by 1 (since
> | ram_find_and_save_block() will be called once), but we might increase
> | xbzrle_counters.cache_miss for 2M/4K=512 times (we'll call
> | save_xbzrle_page() that many times) if all the pages got cache miss.
> | Then IMHO the cache miss rate will be 512/1=51200% (while it should
> | actually be just 100% cache miss).
>
> And he also suggested as xbzrle_counters.cache_miss_rate is the only
> user of rs->iterations we can adapt it to count target guest page
> numbers
>
> After that, rename 'iterations' to 'target_page_count' to better reflect
> its meaning
>
> Suggested-by: Peter Xu <address@hidden>
> Signed-off-by: Xiao Guangrong <address@hidden>
Reviewed-by: Peter Xu <address@hidden>
Thanks,
--
Peter Xu
- [Qemu-devel] [PATCH v4 00/10] migration: compression optimization, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 02/10] migration: fix counting normal page for compression, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 03/10] migration: introduce save_zero_page_to_file, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 04/10] migration: drop the return value of do_compress_ram_page, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 05/10] migration: move handle of zero page to the thread, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 01/10] migration: do not wait for free thread, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 06/10] migration: hold the lock only if it is really needed, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 07/10] migration: do not flush_compressed_data at the end of each iteration, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 08/10] migration: fix calculating xbzrle_counters.cache_miss_rate, guangrong . xiao, 2018/08/21
- Re: [Qemu-devel] [PATCH v4 08/10] migration: fix calculating xbzrle_counters.cache_miss_rate,
Peter Xu <=
- [Qemu-devel] [PATCH v4 10/10] migration: handle the error condition properly, guangrong . xiao, 2018/08/21
- [Qemu-devel] [PATCH v4 09/10] migration: show the statistics of compression, guangrong . xiao, 2018/08/21