changelog --------- v11 - v10 - Addressed all the comments from Thomas Gleixner. - I added one more patch: "x86/tsc: prepare for early sched_clock" which fixes a problem that I discovered while testing. I am not particularly happy with the fix, as it adds a new argument that is used only in one place, but if you have a suggestion for a different approach on how to address this problem please let me know.
v10 - v9 - Added another patch to this series that removes dependency between KVM clock, and memblock allocator. The benefit is that all clocks can now be initialized even earlier. v9 - v8 - Addressed more comments from Dou Liyang v8 - v7 - Addressed comments from Dou Liyang: - Moved tsc_early_init() and tsc_early_fini() to be all inside tsc.c, and changed them to be static. - Removed warning when notsc parameter is used. - Merged with: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git v7 - v6 - Removed tsc_disabled flag, now notsc is equivalent of tsc=unstable - Simplified changes to sched/clock.c, by removing the sched_clock_early() and friends as requested by Peter Zijlstra. We know always use sched_clock() - Modified x86 sched_clock() to return either early boot time or regular. - Added another example why ealry boot time is important v5 - v6 - Added a new patch: time: sync read_boot_clock64() with persistent clock Which fixes missing __init macro, and enabled time discrepancy fix that was noted by Thomas Gleixner - Split "x86/time: read_boot_clock64() implementation" into a separate patch v4 - v5 - Fix compiler warnings on systems with stable clocks. v3 - v4 - Fixed tsc_early_fini() call to be in the 2nd patch as reported by Dou Liyang - Improved comment before __use_sched_clock_early to explain why we need both booleans. - Simplified valid_clock logic in read_boot_clock64(). v2 - v3 - Addressed comment from Thomas Gleixner - Timestamps are available a little later in boot but still much earlier than in mainline. This significantly simplified this work. v1 - v2 In patch "x86/tsc: tsc early": - added tsc_adjusted_early() - fixed 32-bit compile error use do_div() The early boot time stamps were discussed recently in these threads: http://lkml.kernel.org/r/1527672059-6225-1-git-send-email-feng.t...@intel.com http://lkml.kernel.org/r/1527672059-6225-2-git-send-email-feng.t...@intel.com I updated my series to the latest mainline and sending it again. Peter mentioned he did not like patch 6,7, and we can discuss for a better way to do that, but I think patches 1-5 can be accepted separetly, since they already enable early timestamps on platforms where sched_clock() is available early. Such as KVM. Adding early boot time stamps support for x86 machines. SPARC patches for early boot time stamps are already integrated into mainline linux. Sample output ------------- Before: https://paste.ubuntu.com/26133428/ After: https://paste.ubuntu.com/26133523/ For exaples how early time stamps are used, see this work: Example 1: https://lwn.net/Articles/734374/ - Without early boot time stamps we would not know about the extra time that is spent zeroing struct pages early in boot even when deferred page initialization. Example 2: https://patchwork.kernel.org/patch/10021247/ - If early boot timestamps were available, the engineer who introduced this bug would have noticed the extra time that is spent early in boot. Pavel Tatashin (7): x86/tsc: remove tsc_disabled flag time: sync read_boot_clock64() with persistent clock x86/time: read_boot_clock64() implementation sched: early boot clock kvm/x86: remove kvm memblock dependency x86/paravirt: add active_sched_clock to pv_time_ops x86/tsc: use tsc early Example 3: http://lkml.kernel.org/r/20180615155733.1175-1-pasha.tatas...@oracle.com - Needed early time stamps to show improvement Pavel Tatashin (6): x86/tsc: redefine notsc to behave as tsc=unstable kvm/x86: remove kvm memblock dependency time: replace read_boot_clock64() with read_persistent_wall_and_boot_offset() x86/tsc: prepare for early sched_clock. sched: early boot clock x86/tsc: use tsc early .../admin-guide/kernel-parameters.txt | 2 - Documentation/x86/x86_64/boot-options.txt | 4 +- arch/arm/kernel/time.c | 12 +-- arch/s390/kernel/time.c | 11 ++- arch/x86/kernel/kvm.c | 1 + arch/x86/kernel/kvmclock.c | 64 ++----------- arch/x86/kernel/setup.c | 7 +- arch/x86/kernel/tsc.c | 89 +++++++++++-------- include/linux/timekeeping.h | 3 +- kernel/sched/clock.c | 10 ++- kernel/time/timekeeping.c | 61 +++++++------ 11 files changed, 117 insertions(+), 147 deletions(-) -- 2.17.1