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Default branch: MAIN
Revision 1.14 / (download) - annotate - [select for diffs], Sat Feb 4 19:19:35 2023 UTC (16 months ago) by cheloha
Branch: MAIN
CVS Tags: OPENBSD_7_5_BASE,
OPENBSD_7_5,
OPENBSD_7_4_BASE,
OPENBSD_7_4,
OPENBSD_7_3_BASE,
OPENBSD_7_3,
HEAD
Changes since 1.13: +1 -9 lines
Diff to previous 1.13 (colored)
timecounting: remove incomplete PPS support The timecounting code has had stubs for pulse-per-second (PPS) polling since it was imported in 2004. At this point it seems unlikely that anyone is going to finish adding PPS support, so let's remove the stubs: - Delete the dead tc_poll_pps() call from tc_windup(). - Remove all tc_poll_pps symbols from the kernel. Link: https://marc.info/?l=openbsd-tech&m=167519035723210&w=2 ok miod@
Revision 1.13 / (download) - annotate - [select for diffs], Fri Aug 12 02:20:36 2022 UTC (21 months, 4 weeks ago) by cheloha
Branch: MAIN
CVS Tags: OPENBSD_7_2_BASE,
OPENBSD_7_2
Changes since 1.12: +2 -1 lines
Diff to previous 1.12 (colored)
amd64: simplify TSC synchronization testing Computing a per-CPU TSC skew value is error-prone, especially on multisocket machines and VMs. My best guess is that larger latencies appear to the current skew measurement test as TSC desync, and so the TSC is demoted to a kernel timecounter on these machines or marked non-monotonic. This patch eliminates per-CPU TSC skew values. Instead of trying to measure and correct for TSC desync we only try to detect desync, which is less error-prone. This approach should allow a wider variety of machines to use the TSC as a timecounter when running OpenBSD. In the new sync test, both CPUs repeatedly try to detect whether their TSC is trailing the other CPU's TSC. The upside to this approach is that it yields no false positives. The downside to this approach is that it takes more time than the current skew measurement test. Each test round takes 1ms, and we run up to two rounds per CPU, so this patch slows boot down by 2ms per AP. If any CPU fails the sync test, the TSC is marked non-monotonic and a different timecounter is activated. The TC_USER flag remains intact. There is no middle ground where we fall back to only using the TSC in the kernel. Before running the test, we check for the IA32_TSC_ADJUST register and reset it if necessary. This is a trivial way to work around firmware bugs that desync the TSC before we reach the kernel. Unfortunately, at the moment this register appears to only be available on Intel processors. I cannot find an equivalent but differently-named MSR for AMD processors. Because there is no per-CPU skew value, there is also no concept of TSC drift anymore. Miscellaneous notes: - This patch adds a new timecounter utility function, tc_reset_quality(). Used after sync test failure to mark the TSC non-monotonic. - I have left TSC_DEBUG enabled for now. Unsure if we should leave it enabled for release or not. If we disable it we no longer run the sync test after failing it once. Running the test even after failure provides information about the desync on every CPU. - Taking 1ms per test round is fairly conservative. We can experiment with and discuss shorter test rounds. My main goal with a relatively long test round is ensuring VMs actually run the test. It would be bad if a hypervisor interrupted the test for so long that it concealed desync. - The use of two test rounds is mostly a diagnostic tool: it would be very strange if a CPU passed the first round but failed the second. If we ever saw this in the wild it would indicate something odd. - Most of the desync seen in test reports is on Ryzen CPUs. I believe, but cannot prove, that this is due to a widespread firmware bug on AMD motherboards. Hopefully AMD and/or the downstream vendors fix it. - Fixing TSC desync by writing the TSC directly with WRMSR is very difficult. The TSC is a moving target incrementing very quickly and compensating for WRMSR overhead is non-trivial. We can experiment with this, but my confidence is low that we can make it work reliably. Prompted by deraadt@ and kettenis@ in 2021. Shepherded along by deraadt@ throughout. Reprompted by Yuichiro Naito several times. With input from Yuichiro Naito, naddy@, sthen@, dv@, and deraadt@. Tested by florian@, gnezdo@, sthen@, Josh Rickmar, dv@, Mohamed Aslan, Hrvoje Popovski, Yuichiro Naito, semarie@, mlarkin@, asou@, jmatthew@, Renato Aguiar, and Timo Myyra. Patch v1: https://marc.info/?l=openbsd-tech&m=164330092208035&w=2 Patch v2: https://marc.info/?l=openbsd-tech&m=164558519712957&w=2 Patch v3: https://marc.info/?l=openbsd-tech&m=165698681018991&w=2 Patch v4: https://marc.info/?l=openbsd-tech&m=165835507113680&w=2 Patch v5: https://marc.info/?l=openbsd-tech&m=165923705118770&w=2 "just commit it" deraadt@
Revision 1.12 / (download) - annotate - [select for diffs], Mon Jul 6 13:33:09 2020 UTC (3 years, 11 months ago) by pirofti
Branch: MAIN
CVS Tags: OPENBSD_7_1_BASE,
OPENBSD_7_1,
OPENBSD_7_0_BASE,
OPENBSD_7_0,
OPENBSD_6_9_BASE,
OPENBSD_6_9,
OPENBSD_6_8_BASE,
OPENBSD_6_8
Changes since 1.11: +26 -2 lines
Diff to previous 1.11 (colored)
Add support for timeconting in userland. This diff exposes parts of clock_gettime(2) and gettimeofday(2) to userland via libc eliberating processes from the need for a context switch everytime they want to count the passage of time. If a timecounter clock can be exposed to userland than it needs to set its tc_user member to a non-zero value. Tested with one or multiple counters per architecture. The timing data is shared through a pointer found in the new ELF auxiliary vector AUX_openbsd_timekeep containing timehands information that is frequently updated by the kernel. Timing differences between the last kernel update and the current time are adjusted in userland by the tc_get_timecount() function inside the MD usertc.c file. This permits a much more responsive environment, quite visible in browsers, office programs and gaming (apparently one is are able to fly in Minecraft now). Tested by robert@, sthen@, naddy@, kmos@, phessler@, and many others! OK from at least kettenis@, cheloha@, naddy@, sthen@
Revision 1.11 / (download) - annotate - [select for diffs], Sat Jul 4 08:06:08 2020 UTC (3 years, 11 months ago) by anton
Branch: MAIN
Changes since 1.10: +4 -4 lines
Diff to previous 1.10 (colored)
It's been agreed upon that global locks should be expressed using capital letters in locking annotations. Therefore harmonize the existing annotations. Also, if multiple locks are required they should be delimited using commas. ok mpi@
Revision 1.10 / (download) - annotate - [select for diffs], Sat Oct 26 21:16:38 2019 UTC (4 years, 7 months ago) by cheloha
Branch: MAIN
CVS Tags: OPENBSD_6_7_BASE,
OPENBSD_6_7
Changes since 1.9: +4 -1 lines
Diff to previous 1.9 (colored)
clock_getres(2): actually return the resolution of the given clock Currently we return (1000000000 / hz) from clock_getres(2) as the resolution for every clock. This is often untrue. For CPUTIME clocks, if we have a separate statclock interrupt the resolution is (1000000000 / stathz). Otherwise it is as we currently claim: (1000000000 / hz). For the REALTIME/MONOTONIC/UPTIME/BOOTTIME clocks the resolution is that of the active timecounter. During tc_init() we can compute the precision of a timecounter by examining its tc_counter_mask and store it for lookup later in a new member, tc_precision. The resolution of a clock backed by a timecounter "tc" is then tc.tc_precision * (2^64 / tc.tc_frequency) fractional seconds. While here we can clean up sys_clock_getres() a bit. Standards input from guenther@. Lots of input, feedback from kettenis@. ok kettenis@
Revision 1.9 / (download) - annotate - [select for diffs], Wed May 22 19:59:37 2019 UTC (5 years ago) by cheloha
Branch: MAIN
CVS Tags: OPENBSD_6_6_BASE,
OPENBSD_6_6
Changes since 1.8: +4 -2 lines
Diff to previous 1.8 (colored)
SLIST-ify the timecounter list. Call it "tc_list" instead of "timecounters", which is too similar to the variable "timecounter" for my taste. ok mpi@ visa@
Revision 1.8 / (download) - annotate - [select for diffs], Mon Mar 25 23:32:00 2019 UTC (5 years, 2 months ago) by cheloha
Branch: MAIN
CVS Tags: OPENBSD_6_5_BASE,
OPENBSD_6_5
Changes since 1.7: +21 -11 lines
Diff to previous 1.7 (colored)
MP-safe timecounting: new rwlock: tc_lock tc_lock allows adjfreq(2) and the kern.timecounter.hardware sysctl(2) to read/write the active timecounter pointer and the .tc_adj_freq member of the active timecounter safely. This eliminates any possibility of a torn read/write for the .tc_adj_freq member when we drop the KERNEL_LOCK from the timecounting layer. It also ensures the active timecounter does not change in the midst of an adjfreq(2) call. Because these are not high-traffic paths, we can get away with using tc_lock in write-mode to ensure combination read/write adjtime(2) calls are relatively atomic (a) to other writer adjtime(2) calls, and (b) to settimeofday(2)/clock_settime(2) calls, which cancel ongoing adjtime(2) adjustment. When the KERNEL_LOCK is dropped, an unprivileged user will be able to create some tc_lock contention via adjfreq(2); it is very unlikely to ever be a problem. If it ever is actually a problem a lockless read could be added to address it. While here, reorganize sys_adjfreq()/sys_adjtime() to minimize code under the lock. Also while here, make tc_adjfreq() void, as it cannot fail under any circumstance. Also also while here, annotate various globals/struct members with lock ordering details. With lots of input from mpi@ and visa@. ok visa@
Revision 1.7 / (download) - annotate - [select for diffs], Sun Mar 10 21:16:15 2019 UTC (5 years, 3 months ago) by cheloha
Branch: MAIN
Changes since 1.6: +2 -1 lines
Diff to previous 1.6 (colored)
Move adjtimedelta from kern_time.c to kern_tc.c. This will simplify upcoming MP-safety diffs for the timecounting layer. adjtimedelta is now accessed nowhere outside of kern_tc.c, so we can remove its extern declaration from kernel.h. Zeroing adjtimedelta within timecounter_mtx before we jump the real-time clock is also a bit safer than what we do now, as we are not racing a simultaneous tc_windup() call from hardclock(), which itself can modify adjtimedelta via ntp_update_second(). Discussed with visa@ and mpi@. ok visa@
Revision 1.6 / (download) - annotate - [select for diffs], Mon May 28 18:05:42 2018 UTC (6 years ago) by guenther
Branch: MAIN
CVS Tags: OPENBSD_6_4_BASE,
OPENBSD_6_4
Changes since 1.5: +3 -3 lines
Diff to previous 1.5 (colored)
Constipate a bunch of time functions ok tb@ kettenis@
Revision 1.5 / (download) - annotate - [select for diffs], Thu Apr 3 17:58:31 2014 UTC (10 years, 2 months ago) by beck
Branch: MAIN
CVS Tags: OPENBSD_6_3_BASE,
OPENBSD_6_3,
OPENBSD_6_2_BASE,
OPENBSD_6_2,
OPENBSD_6_1_BASE,
OPENBSD_6_1,
OPENBSD_6_0_BASE,
OPENBSD_6_0,
OPENBSD_5_9_BASE,
OPENBSD_5_9,
OPENBSD_5_8_BASE,
OPENBSD_5_8,
OPENBSD_5_7_BASE,
OPENBSD_5_7,
OPENBSD_5_6_BASE,
OPENBSD_5_6
Changes since 1.4: +2 -0 lines
Diff to previous 1.4 (colored)
fix $OpenBSD$, noticed by philip
Revision 1.4 / (download) - annotate - [select for diffs], Thu Apr 3 15:55:29 2014 UTC (10 years, 2 months ago) by beck
Branch: MAIN
Changes since 1.3: +18 -9 lines
Diff to previous 1.3 (colored)
I have discussed these licenses with Poul-Henning Kamp and he has agreed to this license change. We will remember that we all still like beer.
Revision 1.3 / (download) - annotate - [select for diffs], Thu May 24 07:17:42 2012 UTC (12 years ago) by guenther
Branch: MAIN
CVS Tags: OPENBSD_5_5_BASE,
OPENBSD_5_5,
OPENBSD_5_4_BASE,
OPENBSD_5_4,
OPENBSD_5_3_BASE,
OPENBSD_5_3,
OPENBSD_5_2_BASE,
OPENBSD_5_2
Changes since 1.2: +2 -1 lines
Diff to previous 1.2 (colored)
On resume, run forward the monotonic and realtimes clocks instead of jumping just the realtime clock, triggering and adjusting timeouts to reflect that. ok matthew@ deraadt@
Revision 1.2 / (download) - annotate - [select for diffs], Mon Oct 30 20:19:33 2006 UTC (17 years, 7 months ago) by otto
Branch: MAIN
CVS Tags: OPENBSD_5_1_BASE,
OPENBSD_5_1,
OPENBSD_5_0_BASE,
OPENBSD_5_0,
OPENBSD_4_9_BASE,
OPENBSD_4_9,
OPENBSD_4_8_BASE,
OPENBSD_4_8,
OPENBSD_4_7_BASE,
OPENBSD_4_7,
OPENBSD_4_6_BASE,
OPENBSD_4_6,
OPENBSD_4_5_BASE,
OPENBSD_4_5,
OPENBSD_4_4_BASE,
OPENBSD_4_4,
OPENBSD_4_3_BASE,
OPENBSD_4_3,
OPENBSD_4_2_BASE,
OPENBSD_4_2,
OPENBSD_4_1_BASE,
OPENBSD_4_1
Changes since 1.1: +4 -1 lines
Diff to previous 1.1 (colored)
Timecounter based implementation of adjfreq(2). Largely from art@ Tested by various using not (yet) committed amd64 timecounter code. ok deraadt@
Revision 1.1 / (download) - annotate - [select for diffs], Wed Jul 28 17:15:12 2004 UTC (19 years, 10 months ago) by tholo
Branch: MAIN
CVS Tags: OPENBSD_4_0_BASE,
OPENBSD_4_0,
OPENBSD_3_9_BASE,
OPENBSD_3_9,
OPENBSD_3_8_BASE,
OPENBSD_3_8,
OPENBSD_3_7_BASE,
OPENBSD_3_7,
OPENBSD_3_6_BASE,
OPENBSD_3_6
This touches only MI code, and adds new time keeping code. The code is all conditionalized on __HAVE_TIMECOUNTER, and not enabled on any platforms. adjtime(2) support exists, courtesy of nordin@, sysctl(2) support and a concept of quality for each time source attached exists. High quality time sources exists for PIIX4 ACPI timer as well as some AMD power management chips. This will have to be redone once we actually add ACPI support (at that time we need to use the ACPI interfaces to get at these clocks). ok art@ ken@ miod@ jmc@ and many more