Red Hat Bugzilla – Bug 651005
Excessive fpu swap entering and exiting kvm from host userspace
Last modified: 2013-01-09 18:18:51 EST
Description of problem: kvm saves and restores the host fpu, even if the host hasn't been using it. This is inefficient. Version-Release number of selected component (if applicable): 2.6.32-80.el6 How reproducible: Always Steps to Reproduce: 1. Run a guest Actual results: Excessive host fpu save/restores Expected results: Only swap the host fpu when necessary Additional info: Fixed in upstream
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
Patch(es) available on kernel-2.6.32-83.el6
Tried on kernel-2.6.32-122.el6 steps 1.start a RHEL6_64 bit guest with clocksource=acpi_pm 2.run a program that calls gettimeofday() in a loop # cat test.c #include <sys/time.h> void main() { struct timeval tv; while(1) { gettimeofday(&tv,0); } } 3.start system tap to probe save_init_fpu() eg: ## cat save_init_fpu.stp probe begin { printf("start...\n") } probe kernel.function("save_init_fpu") { printf("calling..\n") 4.#stap save_init_fpu.stp Acutal Results I can NOT get the times save_init_fpu() loaded. bcao--->avi, Hi, Could you provide me How to reproduce and verify it ? thanks, Mike
Verified this issue by using code review& functional test on 2.6.32-128.el6 steps for code review: 1.download kernel-2.6.32-130.src.rpm 2.compile the src code to see whether patch included Acutal Results: check linux-2.6.32-130.el6.x86_64/arch/x86/kvm/x86.c , the patch is included. steps for functional testing. 1.start linux guest 2.exec a fpu apps more than 12 hours Actual Results: Guest works good and no crash occurs. Based on above , This issue has been fixed already.change status to VERIFIED.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0542.html