I see the fllowing panic on AMD when exiting pmcstat:
panic: [pmc,1473] pp_pmcval outside of expected range cpu=2 ri=17
pp_pmcval=fffffffffa529f5b pm_reloadcount=10000
It seems that at least on AMD a performance counter keeps counting after
overflowing. When pmcstat exits it sets counters that it used to
PMC_STATE_DELETED and waits until their use count goes to zero.
amd_intr() wouldn't reload a counter in that state and, thus, a counter
would be allowed to overflow. That means that the counter's value would
be allowed to go outside the expected range.
MFC after: 2 weeks
It is possible that wrmsr in amd_stop_pmc() causes an overflow in a counter
that it disables. In that case a non-maskable interrupt is generated. The
interrupt handler code was written in such a way that it would re-enable the
counter. That would lead to an unexpected interrupt later on.
This problem was easy to reproduce with
$ pmcstat -T -P instructions -t $pid
if the target process is sufficiently busy and there are context switches from
time to time. There would be a lot of interrupts to "race" with amd_stop_pmc()
called during the context switches. The problem affected only AMD processors.
While there, trace whether amd_intr() claimed an interrupt.
Reviewed by: jhb
MFC after: 2 weeks
When hwpmc stops sampling it will set the pm_state to something other
than PMC_STATE_RUNNING. This means the following sequence can happen:
CPU 0: Enter the interrupt handler
CPU 0: Set the thread TDP_CALLCHAIN pflag
CPU 1: Stop sampling
CPU 0: Call pmc_process_samples, sampling is stopped so clears ps_nsamples
CPU 0: Finishes interrupt processing with the TDP_CALLCHAIN flag set
CPU 0: Call pmc_capture_user_callchain to capture the user call chain
CPU 0: Find all the pmc sample are free so no call chains need to be captured
CPU 0: KASSERT because of this
This fixes the issue by checking if any of the samples have been stopped
and including this in te KASSERT.
PR: 204273
Reviewed by: bz, gnn
Obtained from: ABT Systems Ltd
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D6581
Currently, Application Processors (non-boot CPUs) are started by
MD code at SI_SUB_CPU, but they are kept waiting in a "pen" until
SI_SUB_SMP at which point they are released to run kernel threads.
SI_SUB_SMP is one of the last SYSINIT levels, so APs don't enter
the scheduler and start running threads until fairly late in the
boot.
This change moves SI_SUB_SMP up to just before software interrupt
threads are created allowing the APs to start executing kernel
threads much sooner (before any devices are probed). This allows
several initialization routines that need to perform initialization
on all CPUs to now perform that initialization in one step rather
than having to defer the AP initialization to a second SYSINIT run
at SI_SUB_SMP. It also permits all CPUs to be available for
handling interrupts before any devices are probed.
This last feature fixes a problem on with interrupt vector exhaustion.
Specifically, in the old model all device interrupts were routed
onto the boot CPU during boot. Later after the APs were released at
SI_SUB_SMP, interrupts were redistributed across all CPUs.
However, several drivers for multiqueue hardware allocate N interrupts
per CPU in the system. In a system with many CPUs, just a few drivers
doing this could exhaust the available pool of interrupt vectors on
the boot CPU as each driver was allocating N * mp_ncpu vectors on the
boot CPU. Now, drivers will allocate interrupts on their desired CPUs
during boot meaning that only N interrupts are allocated from the boot
CPU instead of N * mp_ncpu.
Some other bits of code can also be simplified as smp_started is
now true much earlier and will now always be true for these bits of
code. This removes the need to treat the single-CPU boot environment
as a special case.
As a transition aid, the new behavior is available under a new kernel
option (EARLY_AP_STARTUP). This will allow the option to be turned off
if need be during initial testing. I plan to enable this on x86 by
default in a followup commit in the next few days and to have all
platforms moved over before 11.0. Once the transition is complete,
the option will be removed along with the !EARLY_AP_STARTUP code.
These changes have only been tested on x86. Other platform maintainers
are encouraged to port their architectures over as well. The main
things to check for are any uses of smp_started in MD code that can be
simplified and SI_SUB_SMP SYSINITs in MD code that can be removed in
the EARLY_AP_STARTUP case (e.g. the interrupt shuffling).
PR: kern/199321
Reviewed by: markj, gnn, kib
Sponsored by: Netflix
supported, use full-width aliases MSRs for writes. This fixes the
"[pmc,X] negative increment" assertion on the context switch when
clipped counter value is sign-extended.
Add definitions for the MSR IA32_PERF_CAPABILITIES needed to detect
the feature.
PR: 207068
Submitted by: joss.upton@yahoo.com
MFC after: 2 weeks
when its result is immediately ignored, i.e. for kernel processes
forked from the user process. Do not test for non-null before freeing
string.
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
This is the final step required allowing to compile and to run RISC-V
kernel and userland from HEAD.
RISC-V is a completely open ISA that is freely available to academia
and industry.
Thanks to all the people involved! Special thanks to Andrew Turner,
David Chisnall, Ed Maste, Konstantin Belousov, John Baldwin and
Arun Thomas for their help.
Thanks to Robert Watson for organizing this project.
This project sponsored by UK Higher Education Innovation Fund (HEIF5) and
DARPA CTSRD project at the University of Cambridge Computer Laboratory.
FreeBSD/RISC-V project home: https://wiki.freebsd.org/riscv
Reviewed by: andrew, emaste, kib
Relnotes: Yes
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
Differential Revision: https://reviews.freebsd.org/D4982
IAP_F_FM's as well as incorrect umask specifications for
some of the new Broadwell/Skylake PMC's. Also silvermont
had a *lot* of missing IAP_F_FM.
Sponsored by: Netflix Inc.
tested on the Broadwell-Xeon with a hacked up version of pmcstudy -T. I still need
to circle back and add in to pmcstudy all the new tests from the Broadwell Vtune
guide (for the hacked up version I just made it so I could run the -T option). The
Skylake CPU is not yet available (even though Intel is advertising it .. imagine that).
The Skylake PMC's will need to be tested once we can get a sample skylake CPU :-)
Sponsored by: Netflix Inc.
The code tracks a counter which is the number of events until the next
sample. On context switch in, it loads the saved counter. On context
switch out, it tries to calculate a new saved counter.
Problems:
1. The saved counter was shared by all threads in a process. However, this
means that all threads would be initially loaded with the same saved
counter. However, that could result in sampling more often than once every
X number of events.
2. The calculation to determine a new saved counter was backwards. It
added when it should have subtracted, and subtracted when it should have
added. Assume a single-threaded process with a reload count of 1000 events.
Assuming the counter on context switch in was 100 and the counter on context
switch out was 50 (meaning the thread has "consumed" 50 more events), the
code would calculate a new saved counter of 150 (instead of the proper 50).
Fix:
1. As soon as the saved counter is used to initialize a monitor for a
thread on context switch in, set the saved counter to the reload count.
That way, subsequent threads to use the saved counter will get the full
reload count, assuring we sample at least once every X number of events
(across all threads).
2. Change the calculation of the saved counter. Due to the change to the
saved counter in #1, we simply need to add (modulo the reload count) the
remaining counter time we retrieve from the CPU when a thread is context
switched out.
Differential Revision: https://reviews.freebsd.org/D4122
Approved by: gnn (mentor)
MFC after: 1 month
Sponsored by: Juniper Networks
Changes to the code to gather user stacks:
* Delay setting pmc_cpumask until we actually have the stack.
* When recording user stack traces, only walk the portion of the ring
that should have samples for us.
Sponsored by: Juniper Networks
Approved by: gnn (mentor)
MFC after: 1 month
Currently, there is a single pm_stalled flag that tracks whether a
performance monitor was "stalled" due to insufficent ring buffer
space for samples. However, because the same performance monitor
can run on multiple processes or threads at the same time, a single
pm_stalled flag that impacts them all seems insufficient.
In particular, you can hit corner cases where the code fails to stop
performance monitors during a context switch out, because it thinks
the performance monitor is already stopped. However, in reality,
it may be that only the monitor running on a different CPU was stalled.
This patch attempts to fix that behavior by tracking on a per-CPU basis
whether a PM desires to run and whether it is "stalled". This lets the
code make better decisions about when to stop PMs and when to try to
restart them. Ideally, we should avoid the case where the code fails
to stop a PM during a context switch out.
Sponsored by: Juniper Networks
Reviewed by: jhb
Approved by: gnn (mentor)
Differential Revision: https://reviews.freebsd.org/D4124
according to the Cortex-A8 TRM r3p2 section 3.2.49.
The A8 list differs from the "ARM-v7 common" list, given the A8
was an earlier model.
There is still more work to be done for other Cortex-Ax version as
andrew points out, but I am just trying to fix A8 for now for teaching.
MFC after: 2 weeks
Sponsored by: DARPA/AFRL
Obtained from: Cambridge/L41
Reviewed by: andrew
Differential Revision: https://reviews.freebsd.org/D3876
in the parent, we will inherit the pmcids but cannot execute any operations
on them in the child. The reason for this is that pmc_find_pmc() only
tries to find the current process on the owners hash list, but given the
child does not own the attachment, we cannot find it.
Thus, in case the initial lookup fails, try to find the pmc_process state
affiliated with the child process, lookup the pmc from there using the
row index, and get the owner process from that pmc.
Then continue as normal and lookup the pmc context of the owner (process).
This allows us to call, e.g., pmc_start() in the child process before we
start the work there, but to collect the accumulated results later in
the parent.
Sponsored by: DARPA,AFRL
Obtained from: L41
Tested by: rwatson, L41
MFC after: 4 weeks
Reviewed by: gnn
Differential Revision: https://reviews.freebsd.org/D2052
When providing memory map information to userland, populate the vnode pointer
for tmpfs files. Set the memory mapping to appear as a vnode type, to match
FreeBSD 9 behavior.
This fixes the use of tmpfs files with the dtrace pid provider,
procstat -v, procfs, linprocfs, pmc (pmcstat), and ptrace (PT_VM_ENTRY).
Submitted by: Eric Badger <eric@badgerio.us> (initial revision)
Obtained from: Dell Inc.
PR: 198431
MFC after: 2 weeks
Reviewed by: jhb
Approved by: kib (mentor)
In both cases, the the effect of the bug was that a very small positive
number was written to the counter. This means that a large number of
events needed to occur before the next sampling interrupt would trigger.
Even with very frequently occurring events like clock cycles wrapping all
the way around could take a long time. Both bugs occurred when updating
the saved reload count for an outgoing thread on a context switch.
First, the counter-independent code compares the current reload count
against the count set when the thread switched in and generates a delta
to apply to the saved count. If this delta causes the reload counter
to go negative, it would add a full reload interval to wrap it around to
a positive value. The fix is to add the full reload interval if the
resulting counter is zero.
Second, occasionally the raw counter value read during a context switch
has actually wrapped, but an interrupt has not yet triggered. In this
case the existing logic would return a very large reload count (e.g.
2^48 - 2 if the counter had overflowed by a count of 2). This was seen
both for fixed-function and programmable counters on an E5-2643.
Workaround this case by returning a reload count of zero.
PR: 198149
Differential Revision: https://reviews.freebsd.org/D2557
Reviewed by: emaste
MFC after: 1 week
Sponsored by: Norse Corp, Inc.
This removes one of the frequent causes of ABI breakage when new CPU
types are added to hwpmc(4).
Differential Revision: https://reviews.freebsd.org/D2586
Reviewed by: davide, emaste, gnn (earlier version)
MFC after: 2 weeks
This supports e500v1, e500v2, and e500mc. Tested only on e500v2, but the
performance counters are identical across all, with e500mc having some
additional events.
Relnotes: Yes
These are similar to the mips24k performance counters - some are
available on perfcnt0/3, some are available on perfcnt1/4.
However, the events aren't all the same.
* Add the events, named the same as from Linux oprofile.
* Verify they're the same as "MIPS32(R) 74KTM Processor Core Family
Software User's Manual"; Document Number: MD00519; Revision 01.05.
* Rename INSTRUCTIONS to something else, so it doesn't clash with
the alias INSTRUCTIONS. I'll try to tidy this up later; there
are a few other aliases to add and shuffle around.
Tested:
* QCA9558 SoC (AP135 board) - MIPS74Kc core (no FPU.)
* make universe; where it didn't fail for other reasons.
TODO:
* It'd be nice to support the four performance counters
in at least this hardware, rather than just two.
Reviewed by: bsdimp ("looks good; don't break world".)
common (autogenerated) versions. Removes extra vertical space,
and makes it easier to grep for usage throughout the tree.
Conditionally compile only for arm6 [1] (yes sounds odd but is right).
Submitted by: andrew [1]
Reviewed by: gnn, andrew (ian earlier version I think)
Differential Revision: https://reviews.freebsd.org/D2159
Obtained from: Cambridge/L41
Sponsored by: DARPA, AFRL
the PMC_IN_KERNEL() macro definition.
Add missing macros to extract the return address (LR) from the trapframe.
Discussed with: andrew
Obtained from: Cambridge/L41
Sponsored by: DARPA, AFRL
MFC after: 2 weeks
not on head.. otherwise the file pointer will be NULL and when
you try to do something with it you will crash. Make the #else
be the old capabilites, and then remove the erroneous ifdefs for
11.
MFC after: 1 week (with the other MFC I was going to do until the panic)
The MEM_UOPS_RETIRED actually work the same way as the Sandy
Bridge counters, but the counters were documented in a different
way and that seemed to cause the Ivy Bridge counters to be
implemented incorrectly. Use the same counter definitions as
Sandy Bridge. While I'm here, rename the counters to match
what's documented in the datasheet.
Differential Revision: https://reviews.freebsd.org/D1590
MFC after: 1 month
Sponsored by: Sandvine Inc.
On Sandy Bridge and later, to count branch-related events you
have to or together a mask indicating the type of branch
instruction to count (e.g. direct jump, branch, etc) and a bits
indicating whether to count taken and not-taken branches. The
current counter definitions where defining this bits individually,
so the counters never worked and always just counted 0.
Fix the counter definitions to instead contain the proper
combination of masks. Also update the man pages to reflect the
new counters.
Differential Revision: https://reviews.freebsd.org/D1587
MFC after: 1 month
Sponsored by: Sandvine Inc.
