[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2] x86/vmx: enable PML by default
Since PML series were merged (but disabled by default) we have conducted lots of PML tests (live migration, GUI display) and PML has been working fine, therefore turn it on by default. Document of PML command line is adjusted accordingly as well. Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx> Tested-by: Robert Hu <robert.hu@xxxxxxxxx> Tested-by: Xudong Hao <xudong.hao@xxxxxxxxx> --- v1->v2: Document of PML command line is adjusted accordingly as well. In case you might want some specific performance data to better get convinced to turn PML on by default, I pasted the specjbb performance data (running in guest which was in log-dirty mode) I gathered when I was posting the PML patch series to xen-devel mailing list for review for your reference. ======================== specjbb performance =========================== I measured specjbb performance in guest when guest is in video ram tracking mode (the most usual case I think), and when guest is in global log-dirty mode (I made some change in XL tool to put guest global log-dirty mode infinitely, see below), from which we can see that PML does improved the specjbb performance in guest while guest is in log-dirty mode, and the more frequently dirty pages are queried, the more performance gain we will have. So while PML probably can't speed up live migration process directly, it will be benefical for use cases such as guest memory dirty speed monitoring. - video ram tracking: WP PML 122805 123887 120792 123249 118577 123348 121856 125195 121286 122056 120139 123037 avg 120909 123462 100% 102.11% performance gain: 2.11% - global log-dirty: WP PML 72862 79511 73466 81173 72989 81177 73138 81777 72811 80257 72486 80413 avg 72959 80718 100% 110.63% performance gain: 10.63% Test machine: Boardwell server with 16 CPUs (1.6G) + 4G memory. Xen hypervisor: lastest upstream Xen dom0 kernel: 3.16.0 guest: 4 vcpus + 1G memory. guest os: ubuntu 14.04 with 3.13.0-24-generic kernel. --- docs/misc/xen-command-line.markdown | 2 +- xen/arch/x86/hvm/vmx/vmcs.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown index c103894..47d148a 100644 --- a/docs/misc/xen-command-line.markdown +++ b/docs/misc/xen-command-line.markdown @@ -715,7 +715,7 @@ Controls EPT related features. > `pml` -> Default: `false` +> Default: `true` >> PML is a new hardware feature in Intel's Broadwell Server and further >> platforms which reduces hypervisor overhead of log-dirty mechanism by diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c index 7a7896e..dbf284d 100644 --- a/xen/arch/x86/hvm/vmx/vmcs.c +++ b/xen/arch/x86/hvm/vmx/vmcs.c @@ -64,7 +64,7 @@ integer_param("ple_gap", ple_gap); static unsigned int __read_mostly ple_window = 4096; integer_param("ple_window", ple_window); -static bool_t __read_mostly opt_pml_enabled = 0; +static bool_t __read_mostly opt_pml_enabled = 1; static s8 __read_mostly opt_ept_ad = -1; /* -- 2.5.0 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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