From 2ec16bc0fc7ab544f2d405fd4fdd0d717c5ec0c5 Mon Sep 17 00:00:00 2001 From: Ryan Thibodeaux Date: Fri, 22 Mar 2019 14:29:57 -0400 Subject: x86/xen: Add "xen_timer_slop" command line option Add a new command-line option "xen_timer_slop=" that sets the minimum delta of virtual Xen timers. This commit does not change the default timer slop value for virtual Xen timers. Lowering the timer slop value should improve the accuracy of virtual timers (e.g., better process dispatch latency), but it will likely increase the number of virtual timer interrupts (relative to the original slop setting). The original timer slop value has not changed since the introduction of the Xen-aware Linux kernel code. This commit provides users an opportunity to tune timer performance given the refinements to hardware and the Xen event channel processing. It also mirrors a feature in the Xen hypervisor - the "timer_slop" Xen command line option. [boris: updated comment describing TIMER_SLOP] Signed-off-by: Ryan Thibodeaux Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky --- Documentation/admin-guide/kernel-parameters.txt | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'Documentation/admin-guide/kernel-parameters.txt') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..2623749ae7a3 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5173,6 +5173,13 @@ with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. + xen_timer_slop= [X86-64,XEN] + Set the timer slop (in nanoseconds) for the virtual Xen + timers (default is 100000). This adjusts the minimum + delta of virtualized Xen timers, where lower values + improve timer resolution at the expense of processing + more timer interrupts. + xirc2ps_cs= [NET,PCMCIA] Format: ,,,,,[,[,[,]]] -- cgit v1.2.3