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Re: [Qemu-devel] [PATCH] Output dirty-bytes-rate instead of dirty-pages-


From: Chao Fan
Subject: Re: [Qemu-devel] [PATCH] Output dirty-bytes-rate instead of dirty-pages-rate
Date: Wed, 15 Mar 2017 12:13:58 +0800
User-agent: Mutt/1.8.0 (2017-02-23)

On Tue, Mar 14, 2017 at 12:37:30PM +0000, Daniel P. Berrange wrote:
>On Tue, Mar 14, 2017 at 01:29:43PM +0100, Juan Quintela wrote:
>> Chao Fan <address@hidden> wrote:
>> > In hmp, dirty-bytes-rate is more friendly than dirty-pages-rate.
>> > It's also better for other tools to determine the cpu throttle
>> > value in different architecture.
>> >
>> > Signed-off-by: Chao Fan <address@hidden>
>> > Signed-off-by: Li Zhijian <address@hidden>
>> 
>> I agree with Daniel here, you can't change the meaning of a field.  Look
>> at skipped pages.  It is zero know because it is not used anymore, but
>> we can't drop it.
>> 
>> I think it is better to expose page_size.  We have now
>> 
>> trasferred: bytes
>> total: bytes
>> duplicate: number of zero pages
>> skipped: always zero.
>> normal: number of normal pages
>> normal_bytes: the same  in bytes
>> mbps: megabytes per second?  I can't even remember this one
>> dirty_sync_count: number of times we have go through the whole memory
>> postcopy_requests = number of pages asked by postcopy faults?
>> dirty_pages_rate = pages by some kind of unit
>> 
>> And we haven't yet started with compression or xbzrle.  I think that the
>> best approach at this point is putting everything in pages except the
>> things that don't make sense.
>> 
>> We can put everything on bytes, but then everything is HUGE.
>> 
>> Anyways, what do libvirt/management apps preffer?
>
>Since we have many fields already which are reported as page counts, I
>think just adding page size would be preferrable to having twice as many
>fields reported duplicating bytes + pages.
>
>The only reason to favour duplicating all fields to report bytes, is if
>we needed to vary page size to deal with huge pages (eg if some reported
>pages were 4kb and other reported pages with 2MB). You can easily just
>scale huge pages counts to be "normal"  pages for purpose of reporting
>though.
>Regards,
>Daniel

Hi Juan and Daniel,

I am wondering if it's OK to expose page_size in qmp or hmp, just like
a new command 'info page_size'.
If confirmed´╝îI will make the new patch.

Thanks,
Chao Fan

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