Bug 156378
Summary: | [EMC RHEL 5.0.0 FEAT] kernel dm: Should the QUEUE_CLUSTER_FLAG of a target device's request queue be included in the device-mapper io_restrictions semantics? | ||||||
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Product: | Red Hat Enterprise Linux 5 | Reporter: | Ed Goggin <egoggin> | ||||
Component: | kernel | Assignee: | Alasdair Kergon <agk> | ||||
Status: | CLOSED CURRENTRELEASE | QA Contact: | |||||
Severity: | medium | Docs Contact: | |||||
Priority: | medium | ||||||
Version: | 5.0 | CC: | agk, bmarzins, christophe.varoqui, dmo, dwysocha, jturner, kanderso, kannan_hariharan, lmb, mbroz, perez-kolk_santiago, rkenna, tranlan | ||||
Target Milestone: | --- | Keywords: | FutureFeature | ||||
Target Release: | --- | ||||||
Hardware: | All | ||||||
OS: | Linux | ||||||
Whiteboard: | |||||||
Fixed In Version: | 5.0.0 | Doc Type: | Enhancement | ||||
Doc Text: | Story Points: | --- | |||||
Clone Of: | Environment: | ||||||
Last Closed: | 2006-10-11 12:37:23 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: | |||||||
Bug Depends On: | |||||||
Bug Blocks: | 182355, 186569 | ||||||
Attachments: |
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Description
Ed Goggin
2005-04-29 15:41:11 UTC
The embedded Qlogic FC HBA driver enables page clustering. Likely that all of the FC HBA drivers do. Should only affect large bios since at least the Qlogic FC HBA driver is configured to support an io up to 255 segments. This should handle just shy of a 1MB bio. Need to check how this would interact with the bio splitting and suspend code. There may be a case for deciding whether or not to set it according to the characteristics of the table. Is this request being considered for incorporation into RHEL 4.0 U3? Thanks. -H Is there an update on this Bugzilla? Thanks. -H Hi Alasdair - have you had an opportunity to look into this enhancement request? If so, do you have an update? Thanks. Heather Well Neil Brown has made a patch (which I'll attach and we can test for U4) but I'm not sure it'll make much difference to performance because device-mapper still requires I/O to be broken up into small pieces. This is likely to need block layer changes for which we should create a separate feature request to try to address this issue in the RHEL5 (or might even have to be RHEL6) time frame. Created attachment 124691 [details]
dm-table-queue-cluster.patch
Unfortunately the structures in device-mapper.h weren't designed for extension
and the new 'no_cluster' field forms part of an important exposed structure -
struct dm_target - and this patch will break ABI.
If we decide it is worth putting this in RHEL4 U4, then we need to come up with
a workaround.
I don't think it's worth doing a backport - propose letting the upstream change filter down into RHEL5. What's the status of this? Did the changes land in RHEL5? Yes, they're in the upstream kernel RHEL5 kernel was derived from. Closing out based on comment 26. |