Bug 276581
Summary: | Slowness with Qlogic HCAs | ||
---|---|---|---|
Product: | Red Hat Enterprise Linux 5 | Reporter: | Gurhan Ozen <gozen> |
Component: | openib | Assignee: | Doug Ledford <dledford> |
Status: | CLOSED NOTABUG | QA Contact: | |
Severity: | low | Docs Contact: | |
Priority: | medium | ||
Version: | 5.1 | CC: | jburke |
Target Milestone: | --- | ||
Target Release: | --- | ||
Hardware: | All | ||
OS: | All | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | Bug Fix | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2007-09-04 19:05:22 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
Gurhan Ozen
2007-09-04 16:09:53 UTC
MTRR stands for memory type range register. It is the kernel provided means by which you can configure the motherboard and CPU to do either caching, no caching, or write combining on memory ranges. The error in question means that the ipath driver is attempting to use the general kernel facility for setting the memory type of the IO memory on the card. The CPU in the machine is not allowing the memory type to be set to write combining. Since the ipath cards are mostly software driver based with the driver writing instructions into the cards memory region, it goes much faster when multiple 32bit IO writes are combined into a 32byte burst. This doesn't happen on this machine because the chipset isn't allowing that memory region to be mapped as write combining. All this really means is that the test machine you are using isn't well suited to this card because the motherboard doesn't support what the card needs in order to perform well (and it has nothing to do with RAM size, just motherboard memory mapping capabilities). Closing as NOTABUG. |