Bug 237605
Summary: | [cciss?/HT?] Sequencial-Write-Throughput performance decrease because of an increase of CPU and process/thread in RHEL5 | ||
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Product: | Red Hat Enterprise Linux 5 | Reporter: | Masaki MAENO <maeno.masaki> |
Component: | kernel | Assignee: | Vitaly Mayatskikh <vmayatsk> |
Status: | CLOSED NOTABUG | QA Contact: | Red Hat Kernel QE team <kernel-qe> |
Severity: | medium | Docs Contact: | |
Priority: | medium | ||
Version: | 5.0 | CC: | anton |
Target Milestone: | --- | ||
Target Release: | --- | ||
Hardware: | All | ||
OS: | Linux | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | Bug Fix | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2010-02-10 09:28:21 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
Masaki MAENO
2007-04-24 02:03:01 UTC
I understood that the default value of /sys/block/<device>/queue/nr_requests changes from 8192 (RHEL4) to 128 (RHEL5) is a cause of bad sequential-write performance. I confirmed that the performance improved by making nr_requests 128 to 8192 in hp 4CPU(with DualCore) or 8CPU (2CPU with HT or 2CPU with DualCore and HT). I ran iozone on HP DL385 machine on both RHEL-4.4 and RHEL-5.4 (-pre)and see RHEL4 overcomes RHEL5 in "readers", "re-readers" and "random writers" tests. In all others tests RHEL5 beats RHEL4. When I've changed nr_requests from 128 to 8192, RHEL4 still overcomes RHEL5 in "readers" (10%) and "random writes" (30%) tests. In all other tests RHEL5 is faster, up to 5x. The has been closed due to long inactivity. And as per Comment #2, it's not the subject to fix. Too way much changes between EL4 and EL5, where particular slowdown can't be considered as regression. Thanks! |