[lkml]   [2009]   [Oct]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [Xen-devel] [PATCH 05/12] xen/pvclock: add monotonicity check
On 10/15/09 06:27, Dan Magenheimer wrote:
> I understand but you are now essentially emulating a
> reliable platform timer with a potentially unreliable
> (but still high resolution) per-CPU timer AND probably
> delivering that result to userland.
> Read_tsc should only be used if either CONSTANT_TSC
> or TSC_RELIABLE is true, so read_tsc is guaranteed
> to be monotonically-strictly-increasing by hardware
> (and enforced for CONSTANT_TSC by check_tsc_warp
> at boot).

read_tsc clearly isn't expected to produce absolutely globally monotonic
results; if it were then the check wouldn't be necessary.


 \ /
  Last update: 2009-10-15 21:25    [W:0.118 / U:3.396 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site