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Bug 2048460

Summary:	Migration of Multiterabyte guests spend too much time on bitmap_test_and_clear_atomic()
Product:	Red Hat Enterprise Linux 9	Reporter:	Juan Quintela <quintela>
Component:	qemu-kvm	Assignee:	Juan Quintela <quintela>
qemu-kvm sub component:	Live Migration	QA Contact:	Li Xiaohui <xiaohli>
Status:	CLOSED NOTABUG	Docs Contact:
Severity:	medium
Priority:	medium	CC:	aadam, chayang, coli, jinzhao, juzhang, nilal, nkoenig, virt-maint, yuhuang
Version:	9.0	Keywords:	Triaged
Target Milestone:	rc	Flags:	pm-rhel: mirror+
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2023-04-25 10:03:55 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Juan Quintela 2022-01-31 10:02:12 UTC

Description of problem:

When we are migrating a Multiterabyte machine, we spend 24% of the time on that function.  We only use that function for the clear bitmap.


Version-Release number of selected component (if applicable):

All of them.


How reproducible:

100% with a multiterabyte guests.  We catched it when running HANNA Cool DB test.



Actual results:

There are times when we are not sending anything because we are waiting on the bitmap.

Expected results:

The operations on the bitmap shouldn't be noticed at all.  It is supposed that we only update one bit for each Gigabyte scanned.  We are updating one for each 4K page.

Additional info:

Comment 1 Li Xiaohui 2023-04-04 10:00:46 UTC

Hi Juan, Nitesh

(In reply to Juan Quintela from comment #0)
> Description of problem:
> 
> When we are migrating a Multiterabyte machine, we spend 24% of the time on
> that function.  We only use that function for the clear bitmap.
> 
> 
> Version-Release number of selected component (if applicable):
> 
> All of them.
> 
> 
> How reproducible:
> 
> 100% with a multiterabyte guests.  We catched it when running HANNA Cool DB
> test.
> 
> 
> 
> Actual results:
> 
> There are times when we are not sending anything because we are waiting on
> the bitmap.
> 
> Expected results:
> 
> The operations on the bitmap shouldn't be noticed at all.  It is supposed
> that we only update one bit for each Gigabyte scanned.  We are updating one
> for each 4K page.

According to the expected results, should we add the 'RFE' or 'FutureFeature' keyword for this bug? 
Please do it if I'm right.

> 
> Additional info:

Comment 2 Nitesh Narayan Lal 2023-04-06 16:13:59 UTC

(In reply to Li Xiaohui from comment #1)
> Hi Juan, Nitesh
> 
> (In reply to Juan Quintela from comment #0)
> > Description of problem:
> > 
> > When we are migrating a Multiterabyte machine, we spend 24% of the time on
> > that function.  We only use that function for the clear bitmap.
> > 
> > 
> > Version-Release number of selected component (if applicable):
> > 
> > All of them.
> > 
> > 
> > How reproducible:
> > 
> > 100% with a multiterabyte guests.  We catched it when running HANNA Cool DB
> > test.
> > 
> > 
> > 
> > Actual results:
> > 
> > There are times when we are not sending anything because we are waiting on
> > the bitmap.
> > 
> > Expected results:
> > 
> > The operations on the bitmap shouldn't be noticed at all.  It is supposed
> > that we only update one bit for each Gigabyte scanned.  We are updating one
> > for each 4K page.
> 
> According to the expected results, should we add the 'RFE' or
> 'FutureFeature' keyword for this bug? 

Does look like an RFE. Let's wait for Juan to confirm.

Comment 3 Li Xiaohui 2023-04-12 06:24:08 UTC

Hi Juan, 
As discussed in yesterday's Live migration meeting, please help to cLose the BZ. Thanks.

Comment 4 Juan Quintela 2023-04-25 10:03:55 UTC

Hi
This is a new feature, and I have "fixed" it someother way.
We can close it.

Comment 5 Li Xiaohui 2023-04-25 10:05:30 UTC

Thanks Juan.

Mark qe_test_coverage- due to it's notabug.