Bug 64404

Summary:	increased latency causes drops in video capture
Product:	[Retired] Red Hat Raw Hide	Reporter:	Monty Walls <mwalls>
Component:	kernel	Assignee:	Dave Jones <davej>
Status:	CLOSED WONTFIX	QA Contact:	Brian Brock <bbrock>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	1.0	CC:	pfrields
Target Milestone:	---
Target Release:	---
Hardware:	athlon
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2004-10-30 03:51:00 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Monty Walls 2002-05-03 17:36:28 UTC

From Bugzilla Helper:
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Description of problem:
I use avifile to divx capture tv to disk at 320x240.  Under
2.4.9-31 & 2.4.3 I can capture/compress without frame drops, but under
kernel-2.4.18-22 & 26 I get 2-3% frame drops which seem to be tied to
disk flushing activity.

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


How reproducible:
Always

Steps to Reproduce:
1.grab athlon with scsi disk subsystem (u2w striped)
2.install avifile0.7-20020426 
3.capture 5minutes at 320x240 fps divx4 (low-motion) 
4.review frame drops 
	

Actual Results:  Under 2.4.9 I get less that 1% (13 out of 4200 frames captured)
dropped
Under 2.4.18 I get about 2-3% drops in bursts clustered arround scsi-disk io. 
By contrast my 2.4.3 kernel system (K7-800 ide disk) drops 4 frames in a hour.

Additional info:

As near as I can tell, this tied to the new VM subsystem, based on
the frame drops not occuring under prior kernel releases
(I used 2.2.19 & 2.4.3 also with no frame drops).  So despite Morton's
low-latency patch in 2.4.18-22/26, there appears to be issues still
with the VM subsystem flushing buffers to disk. I can aggravate the
issue by adjusting the bdflush parameters, but can't prevent it.