Re: [PATCH] hmp: Add "calc_dirty_rate" and "info dirty_rate" cmds

From: Peter Xu <peterx@redhat.com>
To: Hyman <huangy81@chinatelecom.cn>
Cc: Chuan Zheng <zhengchuan@huawei.com>,
	Juan Quintela <quintela@redhat.com>,
	qemu-devel@nongnu.org,
	Leonardo Bras Soares Passos <lsoaresp@redhat.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [PATCH] hmp: Add "calc_dirty_rate" and "info dirty_rate" cmds
Date: Tue, 1 Jun 2021 10:36:14 -0400	[thread overview]
Message-ID: <YLZF3v+RrK1D44X7@t490s> (raw)
In-Reply-To: <024ee4df-07a5-a31d-7b97-31d36dfa3ce6@chinatelecom.cn>

On Tue, Jun 01, 2021 at 10:08:31PM +0800, Hyman wrote:
> 
> 
> 在 2021/6/1 8:57, Peter Xu 写道:
> > These two commands are missing when adding the QMP sister commands.  Add them,
> > so developers can play with them easier.
> > 
> > Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > Cc: Juan Quintela <quintela@redhat.com>
> > Cc: Leonardo Bras Soares Passos <lsoaresp@redhat.com>
> > Cc: Chuan Zheng <zhengchuan@huawei.com>
> > Cc: huangy81@chinatelecom.cn
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> > PS: I really doubt whether this is working as expected... I ran one 200MB/s
> > workload inside, what I measured is 20MB/s with current algorithm...  Sampling
> > 512 pages out of 1G mem is not wise enough I guess, especially that assumes
> > dirty workload is spread across the memories while it's normally not the case..
> I doubt whether the sampling can cope with the situation that the guest
> dirty memory too fast so that the sampling within a given time can not
> finish, this may happens when vm is in large scale.

Not my case, though..  I'm with a 1G super small VM, starting a malloc()
workload with 200MB, dirty rate 200MB/s.  As I said in the other thread, I
think it's the algorithm that may not really work well with such workload,
while it could be one of the major workloads..

-- 
Peter Xu