diff options
| author |   Pavel Tatashin <pasha.tatashin@oracle.com> | 2018-07-19 16:55:30 -0400 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2018-07-20 00:02:39 +0200 |
| commit | fe9af81e524e8a86bdd59c0cc0d9e2b0ccaf840f (patch) | |
| tree | 9b9a206a63e6cad4b94bcd96ad03a14cfaa81316 /Documentation/x86/x86_64 | |
| parent | x86/CPU: Call detect_nopl() only on the BSP (diff) | |
| download | linux-dev-fe9af81e524e8a86bdd59c0cc0d9e2b0ccaf840f.tar.xz linux-dev-fe9af81e524e8a86bdd59c0cc0d9e2b0ccaf840f.zip | |
x86/tsc: Redefine notsc to behave as tsc=unstable
Currently, the notsc kernel parameter disables the use of the TSC by
sched_clock(). However, this parameter does not prevent the kernel from
accessing tsc in other places.
The only rationale to boot with notsc is to avoid timing discrepancies on
multi-socket systems where TSC are not properly synchronized, and thus
exclude TSC from being used for time keeping. But that prevents using TSC
as sched_clock() as well, which is not necessary as the core sched_clock()
implementation can handle non synchronized TSC based sched clocks just
fine.
However, there is another method to solve the above problem: booting with
tsc=unstable parameter. This parameter allows sched_clock() to use TSC and
just excludes it from timekeeping.
So there is no real reason to keep notsc, but for compatibility reasons the
parameter has to stay. Make it behave like 'tsc=unstable' instead.
[ tglx: Massaged changelog ]
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-12-pasha.tatashin@oracle.com
Diffstat (limited to 'Documentation/x86/x86_64')
| -rw-r--r-- | Documentation/x86/x86_64/boot-options.txt | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt index 8d109ef67ab6..66114ab4f9fe 100644 --- a/Documentation/x86/x86_64/boot-options.txt +++ b/Documentation/x86/x86_64/boot-options.txt @@ -92,9 +92,7 @@ APICs Timing notsc - Don't use the CPU time stamp counter to read the wall time. - This can be used to work around timing problems on multiprocessor systems - with not properly synchronized CPUs. + Deprecated, use tsc=unstable instead. nohpet Don't use the HPET timer. |