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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <20170327104650.GL11497@pxdev.xzpeter.org> (Peter Xu's message of
	"Mon, 27 Mar 2017 18:46:50 +0800")
References: <20170323204544.12015-1-quintela@redhat.com>
	<20170323204544.12015-17-quintela@redhat.com>
	<20170327104650.GL11497@pxdev.xzpeter.org>
Reply-To: quintela@redhat.com
Date: Tue, 28 Mar 2017 20:34:40 +0200
Message-ID: <874lydqmgv.fsf@secure.mitica>
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Subject: Re: [Qemu-devel] [PATCH 16/51] ram: Move iterations into RAMState
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To: Peter Xu <peterx@redhat.com>
Cc: qemu-devel@nongnu.org, dgilbert@redhat.com

Peter Xu <peterx@redhat.com> wrote:
> On Thu, Mar 23, 2017 at 09:45:09PM +0100, Juan Quintela wrote:
>> Signed-off-by: Juan Quintela <quintela@redhat.com>

>> @@ -693,13 +694,13 @@ static void migration_bitmap_sync(RAMState *rs)
>>          }
>>  
>>          if (migrate_use_xbzrle()) {
>> -            if (rs->iterations_prev != acct_info.iterations) {
>> +            if (rs->iterations_prev != rs->iterations) {
>>                  acct_info.xbzrle_cache_miss_rate =
>>                     (double)(acct_info.xbzrle_cache_miss -
>>                              rs->xbzrle_cache_miss_prev) /
>> -                   (acct_info.iterations - rs->iterations_prev);
>> +                   (rs->iterations - rs->iterations_prev);
>
> Here we are calculating cache miss rate by xbzrle_cache_miss and
> iterations. However looks like xbzrle_cache_miss is counted per guest
> page (in save_xbzrle_page()) while the iteration count is per host
> page (in ram_save_iterate()). Then, what if host page size not equals
> to guest page size? E.g., when host uses 2M huge pages, host page size
> is 2M, while guest page size can be 4K?

Good catch.  Will have to think about this.  You are right.  I will
change that later.

Thanks, Juan.