A shared counter is added in the thread context to track the total number of
streams created on the thread. This number is then reported in stats. It
will be a useful information to diagnose some bugs.
A shared counter is added in the thread context to track the current number
of streams. This number is then reported in stats. It will be a useful
information to diagnose some bugs.
Now we collect this clock in clock_local_update_date(), the closest from
the poller, which is also used when busy-polling, and the values is set
into the thread's curr_mono_time which did not exist before. Later,
clock_leaving_poll() just sets the prev_mono_time value from the curr_
one instead of retrieving the time at this specific point. It also means
that the monotonic time will now also cover the time needed to update
the global time, which should be negligible. Note that we don't collect
the CPU time in the clock_local_update_date() function even though it's
tempting, because when doing busy-polling, it would be collected on each
round while being useless.
Doing so will make sure that the local time always knows the monotonic
time when it is available.
The buffer reserve set by tune.buffers.reserve has long been unused, and
in order to deal gracefully with failed memory allocations we'll need to
resort to a few emergency buffers that are pre-allocated per thread.
These buffers are only for emergency use, so every time their count is
below the configured number a b_free() will refill them. For this reason
their count can remain pretty low. We changed the default number from 2
to 4 per thread, and the minimum value is now zero (e.g. for low-memory
systems). The tune.buffers.limit setting has always been a problem when
trying to deal with the reserve but now we could simplify it by simply
pushing the limit (if set) to match the reserve. That was already done in
the past with a static value, but now with threads it was a bit trickier,
which is why the per-thread allocators increment the limit on the fly
before allocating their own buffers. This also means that the configured
limit is saner and now corresponds to the regular buffers that can be
allocated on top of emergency buffers.
At the moment these emergency buffers are not used upon allocation
failure. The only reason is to ease bisecting later if needed, since
this commit only has to deal with resource management.
The introduction of buffer_wq[] in thread_ctx pushed a few fields around
and the cache line alignment is less satisfying. And more importantly, even
before this, all the lists in the local parts were 8-aligned, with the first
one split across two cache lines.
We can do better:
- sched_profile_entry is not atomic at all, the data it points to is
atomic so it doesn't need to be in the atomic-only region, and it can
fill the 8-hole before the lists
- the align(2*void) that was only before tasklets[] moves before all
lists (and it's a nop for now)
This now makes the lists and buffer_wq[] start on a cache line boundary,
leaves 48 bytes after the lists before the atomic-only cache line, and
leaves a full cache line at the end for 128-alignment. This way we still
have plenty of room in both parts with better aligned fields.
Let's turn the buffer_wq into an array of 4 list heads. These are chosen
by criticality. The DB_CRIT_TO_QUEUE() macro maps each criticality level
into one of these 4 queues. The goal here clearly is to make it possible
to wake up the most critical queues in priority in order to let some tasks
finish their job and release buffers that others can use.
In order to avoid having to look up all queues, a bit map indicates which
queues are in use, which also allows to avoid looping in the most common
case where queues are empty..
Now the rings have one wait queue per group. This should limit the
contention on systems such as EPYC CPUs where the performance drops
dramatically when using more than one CCX.
Tests were run with different numbers and it was showed that value
6 outperforms all other ones at 12, 24, 48, 64 and 80 threads on an
EPYC, a Xeon and an Ampere CPU. Value 7 sometimes comes close and
anything around these values degrades quickly. The value has been
left tunable in the global section.
This commit only introduces everything needed to set up the queue count
so that it's easier to adjust it in the forthcoming patches, but it was
initially added after the series, making it harder to compare.
It was also shown that trying to group the threads in queues by their
thread groups is counter-productive and that it was more efficient to
do that by applying a modulo on the thread number. As surprising as it
seems, it does have the benefit of well balancing any number of threads.
Add a new member <nb_rhttp_conns> in thread_ctx structure. Its purpose
is to count the current number of opened reverse HTTP connections
regarding from their listeners membership.
This patch will be useful to support multi-thread for active reverse
HTTP, in order to select the less loaded thread.
Note that despite access to <nb_rhttp_conns> are only done by the
current thread, atomic operations are used. This is because once
multi-thread support will be added, external threads will also retrieve
values from others.
When debugging a core, it's difficult to match a given gdb thread number
against an internal thread. Let's just store the pthread ID and the stack
pointer in each tinfo. This could help in the future by allowing to just
glance over them and pick the right one depending what info is found
first.
The progressive adoption of OpenSSL 3 and its abysmal handshake
performance has started to reveal situations where it simply isn't
possible anymore to succesfully run health checks on many servers,
because between the moment all the checks are started and the moment
the handshake finally completes, the timeout has expired!
This also has consequences on production traffic which gets
significantly delayed as well, all that for lots of checks. While it's
possible to increase the check delays, it doesn't solve everything as
checks still take a huge amount of time to converge in such conditions.
Here we take a different approach by permitting to enforce the maximum
concurrent checks per thread limitation and implementing an ordered
queue. Thanks to this, if a thread about to start a check has reached
its limit, it will add the check at the end of a queue and it will be
processed once another check is finished. This proves to be extremely
efficient, with all checks completing in a reasonable amount of time
and not being disturbed by the rest of the traffic from other checks.
They're just cycling slower, but at the speed the machine can handle.
One must understand however that if some complex checks perform multiple
exchanges, they will take a check slot for all the required duration.
This is why the limit is not enforced by default.
Tests on SSL show that a limit of 5-50 checks per thread on local
servers gives excellent results already, so that could be a good starting
point.
Let's keep two check counters per thread:
- one for "active" checks, i.e. checks that are no more sleeping
and are assigned to the thread. These include sleeping and
running checks ;
- one for "running" checks, i.e. those which are currently
executing on the thread.
By doing so, we'll be able to spread the health checks load a bit better
and refrain from sending too many at once per thread. The counters are
atomic since a migration increments the target thread's active counter.
These numbers are reported in "show activity", which allows to check
per thread and globally how many checks are currently pending and running
on the system.
Ideally, we should only consider checks in the process of establishing
a connection since that's really the expensive part (particularly with
OpenSSL 3.0). But the inner layers are really not suitable to doing
this. However knowing the number of active checks is already a good
enough hint.
The thread dump mechanism that is used by "show threads" and by the
panic dump is overly complicated due to an initial misdesign. It
firsts wakes all threads, then serializes their dumps, then releases
them, while taking extreme care not to face colliding dumps. In fact
this is not what we need and it reached a limit where big machines
cannot dump all their threads anymore due to buffer size limitations.
What is needed instead is to be able to dump *one* thread, and to let
the requester iterate on all threads.
That's what this patch does. It adds the thread_dump_buffer to the
struct thread_ctx so that the requester offers the buffer to the
thread that is about to be dumped. This buffer also serves as a lock.
A thread at rest has a NULL, a valid pointer indicates the thread is
using it, and 0x1 (NULL+1) is used by the dumped thread to tell the
requester it's done. This makes sure that a given thread is dumped
once at a time. In addition to this, the calling thread decides
whether it accesses the thread by itself or via the debug signal
handler, in order to get a backtrace. This is much saner because the
calling thread is free to do whatever it wants with the buffer after
each thread is dumped, and there is no dependency between threads,
once they've dumped, they're free to continue (and possibly to dump
for another requester if needed). Finally, when the THREAD_DUMP
feature is disabled and the debug signal is not used, the requester
accesses the thread by itself like before.
For now we still have the buffer size limitation but it will be
addressed in future patches.
We're only checking for 0, 1, or >1 groups enabled there, and we'll soon
need to be more precise and know quickly which groups are non-empty.
Let's just replace the count with a mask of enabled groups. This will
allow to quickly spot the presence of any such group in a set.
When a CONNECTION_CLOSE is emitted or received, a QUIC connection enters
respectively in draining or closing state. These states are a loose
equivalent of TCP TIME_WAIT. No data can be exchanged anymore but the
connection is maintained during a certain timer to handle packet
reordering or loss.
A new global list has been defined for QUIC connections in
closing/draining state inside thread_ctx structure. Each time a
connection enters in one of this state, it will be moved from the
default global list to the new closing list.
The objective of this patch is to quickly filter connections on
closing/draining. Most notably, this will be used to wake up these
connections and avoid that haproxy process stopping is delayed by them.
A dedicated function qc_detach_th_ctx_list() has been implemented to
transfer a quic-conn from one list instance to the other. This takes
care of back-references attach to a quic-conn instance in case of a
running "show quic".
This should be backported up to 2.7.
Several times during debugging it has been difficult to find a way to
reliably indicate if a thread had been started and if it was still
running. It's really not easy because the elements we look at are not
necessarily reliable (e.g. harmless bit or idle bit might not reflect
what we think during a signal). And such notions can be subjective
anyway.
Here we define two thread flags, TH_FL_STARTED which is set as soon as
a thread enters run_thread_poll_loop() and drops the idle bit, and
another one, TH_FL_IN_LOOP, which is set when entering run_poll_loop()
and cleared when leaving it. This should help init/deinit code know
whether it's called from a non-initialized thread (i.e. tid must not
be trusted), or shared functions know if they're being called from a
running thread or from init/deinit code outside of the polling loop.
Implement a basic "show quic" CLI handler. This command will be useful
to display various information on all the active QUIC frontend
connections.
This work is heavily inspired by "show sess". Most notably, a global
list of quic_conn has been introduced to be able to loop over them. This
list is stored per thread in ha_thread_ctx.
Also add three CLI handlers for "show quic" in order to allocate and
free the command context. The dump handler runs on thread isolation.
Each quic_conn is referenced using a back-ref to handle deletion during
handler yielding.
For the moment, only a list of raw quic_conn pointers is displayed. The
handler will be completed over time with more information as needed.
This should be backported up to 2.7.
The purpose is to be able to store large thread sets, defined by ranges
that may cross group boundaries, as well as define lists of groups and
masks. The thread_set struct implements the storage, and the parser is
in parse_thread_set(), with a focus on "bind" lines, but not only.
During multiple tests we've already noticed that shared stats counters
have become a real bottleneck under large thread counts. With QUIC it's
pretty visible, with qc_snd_buf() taking 2.5% of the CPU on a 48-thread
machine at only 25 Gbps, and this CPU is entirely spent in the atomic
increment of the byte count and byte rate. It's also visible in H1/H2
but slightly less since we're working with larger buffers, hence less
frequent updates. These counters are exclusively used to report the
byte count in "show info" and the byte rate in the stats.
Let's move them to the thread_ctx struct and make the stats reader
just collect each thread's stats when requested. That's way more
efficient than competing on a single cache line.
After this, qc_snd_buf has totally disappeared from the perf profile
and tests made in h1 show roughly 1% performance increase on small
objects.
The issue addressed by commit fbb934da9 ("BUG/MEDIUM: stick-table: fix
a race condition when updating the expiration task") is still present
when thread groups are enabled, but this time it lies in the scheduler.
What happens is that a task configured to run anywhere might already
have been queued into one group's wait queue. When updating a stick
table entry, sometimes the task will have to be dequeued and requeued.
For this a lock is taken on the current thread group's wait queue lock,
but while this is necessary for the queuing, it's not sufficient for
dequeuing since another thread might be in the process of expiring this
task under its own group's lock which is different. This is easy to test
using 3 stick tables with 1ms expiration, 3 track-sc rules and 4 thread
groups. The process crashes almost instantly under heavy traffic.
One approach could consist in storing the group number the task was
queued under in its descriptor (we don't need 32 bits to store the
thread id, it's possible to use one short for the tid and another
one for the tgrp). Sadly, no safe way to do this was figured, because
the race remains at the moment the thread group number is checked, as
it might be in the process of being changed by another thread. It seems
that a working approach could consist in always having it associated
with one group, and only allowing to change it under this group's lock,
so that any code trying to change it would have to iterately read it
and lock its group until the value matches, confirming it really holds
the correct lock. But this seems a bit complicated, particularly with
wait_expired_tasks() which already uses upgradable locks to switch from
read state to a write state.
Given that the shared tasks are not that common (stick-table expirations,
rate-limited listeners, maybe resolvers), it doesn't seem worth the extra
complexity for now. This patch takes a simpler and safer approach
consisting in switching back to a single wq_lock, but still keeping
separate wait queues. Given that shared wait queues are almost always
empty and that otherwise they're scanned under a read lock, the
contention remains manageable and most of the time the lock doesn't
even need to be taken since such tasks are not present in a group's
queue. In essence, this patch reverts half of the aforementionned
patch. This was tested and confirmed to work fine, without observing
any performance degradation under any workload. The performance with
8 groups on an EPYC 74F3 and 3 tables remains twice the one of a
single group, with the contention remaining on the table's lock first.
No backport is needed.
The profile entry that corresponds to the current task/tasklet being
profiled is now stored into the thread's context. This will allow it
to be accessed from the tasks themselves. This is needed for an upcoming
fix.
When task profiling is enabled, the scheduler can measure and report
the cumulated time spent in each task and their respective latencies. But
this was wrong for tasks with few wakeups as well as for self-waking ones,
because the call date needed to measure how long it takes to process the
task is retrieved in the task itself (->wake_date was turned to the call
date), and we could face two conditions:
- a new wakeup while the task is executing would reset the ->wake_date
field before returning and make abnormally low values being reported;
that was likely the case for taskrun_applet for self-waking applets;
- when the task dies, NULL is returned and the call date couldn't be
retrieved, so that CPU time was not being accounted for. This was
particularly visible with process_stream() which is usually called
only twice per request, and whose time was systematically halved.
The cleanest solution here is to keep in mind that the scheduler already
uses quite a bit of local context in th_ctx, and place the intermediary
values there so that they cannot vanish. The wake_date has to be reset
immediately once read, and only its copy is used along the function. Note
that this must be done both for tasks and tasklet, and that until recently
tasklets were also able to report wrong values due to their sole dependency
on TH_FL_TASK_PROFILING between tests.
One nice benefit for future improvements is that such information will now
be available from the task without having to be stored into the task itself
anymore.
Since the tasklet part was computed on wrapping 32-bit arithmetics and
the task one was on 64-bit, the values were now consistently moved to
32-bit as it's already largely sufficient (4s spent in a task is more
than twice what the watchdog would tolerate). Some further cleanups might
be necessary, but the patch aimed at staying minimal.
Task profiling output after 1 million HTTP request previously looked like
this:
Tasks activity:
function calls cpu_tot cpu_avg lat_tot lat_avg
h1_io_cb 2012338 4.850s 2.410us 12.91s 6.417us
process_stream 2000136 9.594s 4.796us 34.26s 17.13us
sc_conn_io_cb 2000135 1.973s 986.0ns 30.24s 15.12us
h1_timeout_task 137 - - 2.649ms 19.34us
accept_queue_process 49 152.3us 3.107us 321.7yr 6.564yr
main+0x146430 7 5.250us 750.0ns 25.92us 3.702us
srv_cleanup_idle_conns 1 559.0ns 559.0ns 918.0ns 918.0ns
task_run_applet 1 - - 2.162us 2.162us
Now it looks like this:
Tasks activity:
function calls cpu_tot cpu_avg lat_tot lat_avg
h1_io_cb 2014194 4.794s 2.380us 13.75s 6.826us
process_stream 2000151 20.01s 10.00us 36.04s 18.02us
sc_conn_io_cb 2000148 2.167s 1.083us 32.27s 16.13us
h1_timeout_task 198 54.24us 273.0ns 3.487ms 17.61us
accept_queue_process 52 158.3us 3.044us 409.9us 7.882us
main+0x1466e0 18 16.77us 931.0ns 63.98us 3.554us
srv_cleanup_toremove_conns 8 282.1us 35.26us 546.8us 68.35us
srv_cleanup_idle_conns 3 149.2us 49.73us 8.131us 2.710us
task_run_applet 3 268.1us 89.38us 11.61us 3.871us
Note the two-fold difference on process_stream().
This feature is essentially used for debugging so it has extremely limited
impact. However it's used quite a bit more in bug reports and it would be
desirable that at least 2.6 gets this fix backported. It depends on at least
these two previous patches which will then also have to be backported:
MINOR: task: permanently enable latency measurement on tasklets
CLEANUP: task: rename ->call_date to ->wake_date
This one is only used as a hint to improve scheduling latency, so there
is no more point in keeping it global since each thread group handles
its own run q
Their migration was postponed for convenience only but now's time for
having the shared wait queues per thread group and not just per process,
otherwise the WQ lock uses a huge amount of CPU alone.
thread_isolate() and thread_isolate_full() were relying on a set of thread
masks for all threads in different states (rdv, harmless, idle). This cannot
work anymore when the number of threads increases beyond LONGBITS so we need
to change the mechanism.
What is done here is to have a counter of requesters and the number of the
current isolated thread. Threads which want to isolate themselves increment
the request counter and wait for all threads to be marked harmless (or idle)
by scanning all groups and watching the respective masks. This is possible
because threads cannot escape once they discover this counter, unless they
also want to isolate and possibly pass first. Once all threads are harmless,
the requesting thread tries to self-assign the isolated thread number, and
if it fails it loops back to checking all threads. If it wins it's guaranted
to be alone, and can drop its harmless bit, so that other competing threads
go back to the loop waiting for all threads to be harmless. The benefit of
proceeding this way is that there's very little write contention on the
thread number (none during work), hence no cache line moves between caches,
thus frozen threads do not slow down the isolated one.
Once it's done, the isolated thread resets the thread number (hence lets
another thread take the place) and decrements the requester count, thus
possibly releasing all harmless threads.
With this change there's no more need for any global mask to synchronize
any thread, and we only need to loop over a number of groups to check
64 threads at a time per iteration. As such, tinfo's threads_want_rdv
could be dropped.
This was tested with 64 threads spread into 2 groups, running 64 tasks
(from the debug dev command), 20 "show sess" (thread_isolate()), 20
"add server blah/blah" (thread_isolate()), and 20 "del server blah/blah"
(thread_isolate_full()). The load remained very low (limited by external
socat forks) and no stuck nor starved thread was found.
Stopping threads need a mask to figure who's still there without scanning
everything in the poll loop. This means this will have to be per-group.
And we also need to have a global stopping groups mask to know what groups
were already signaled. This is used both to figure what thread is the first
one to catch the event, and which one is the first one to detect the end of
the last job. The logic isn't changed, though a loop is required in the
slow path to make sure all threads are aware of the end.
Note that for now the soft-stop still takes time for group IDs > 1 as the
poller is not yet started on these threads and needs to expire its timeout
as there's no way to wake it up. But all threads are eventually stopped.
The thread group info is not sufficient to represent a thread group's
current state as it's read-only. We also need something comparable to
the thread context to represent the aggregate state of the threads in
that group. This patch introduces ha_tgroup_ctx[] and tg_ctx for this.
It's indexed on the group id and must be cache-line aligned. The thread
masks that were global and that do not need to remain global were moved
there (want_rdv, harmless, idle).
Given that all the masks placed there now become group-specific, the
associated thread mask (tid_bit) now switches to the thread's local
bit (ltid_bit). Both are the same for nbtgroups 1 but will differ for
other values.
There's also a tg_ctx pointer in the thread so that it can be reached
from other threads.
In order to replace the global "all_threads_mask" we'll need to have an
equivalent per group. Take this opportunity for calling it threads_enabled
and make sure which ones are counted there (in case in the future we allow
to stop some).
Now that the tgid is accessible from the thread, it's pointless to have
it in the group, and it was only set but never used. However we'll soon
frequently need the mask corresponding to the group ID and the risk of
getting it wrong with the +1 or to shift 1 instead of 1UL is important,
so let's store the tgid_bit there.
At several places we're dereferencing the thread group just to catch
the group number, and this will become even more required once we start
to use per-group contexts. Let's just add the tgid in the thread_info
struct to make this easier.
Every single place where sleeping_thread_mask was still used was to test
or set a single thread. We can now add a per-thread flag to indicate a
thread is sleeping, and remove this shared mask.
The wake_thread() function now always performs an atomic fetch-and-or
instead of a first load then an atomic OR. That's cleaner and more
reliable.
This is not easy to test, as broadcast FD events are rare. The good
way to test for this is to run a very low rate-limited frontend with
a listener that listens to the fewest possible threads (2), and to
send it only 1 connection at a time. The listener will periodically
pause and the wakeup task will sometimes wake up on a random thread
and will call wake_thread():
frontend test
bind :8888 maxconn 10 thread 1-2
rate-limit sessions 5
Alternately, disabling/enabling a frontend in loops via the CLI also
broadcasts such events, but they're more difficult to observe since
this is causing connection failures.
Right now when an inter-thread wakeup happens, we preliminary check if the
thread was asleep, and if so we wake the poller up and remove its bit from
the sleeping mask. That's not very clean since the sleeping mask cannot be
entirely trusted since a thread that's about to wake up will already have
its sleeping bit removed.
This patch adds a new per-thread flag (TH_FL_NOTIFIED) to remember that a
thread was notified to wake up. It's cleared before checking the task lists
last, so that new wakeups can be considered again (since wake_thread() is
only used to notify about task wakeups and FD polling changes). This way
we do not need to modify a remote thread's sleeping mask anymore. As such
wake_thread() now only tests and sets the TH_FL_NOTIFIED flag but doesn't
clear sleeping anymore.
The thread flags were once believed to be local to the thread, but as
it stands, even the STUCK flag is shared since it's looked at by the
watchdog. As such we'll need to use atomic ops to manipulate them, and
likely to move them into the shared area.
This patch only moves the flag into the shared area so that we can later
decide whether it's best to leave them there or to move them back to the
local area. Interestingly, some tests have shown a 3% better performance
on dequeuing with this, while they're not used by other threads yet, so
there are definitely alignment effects that might change over time.
Since we only use the shared runqueue to put tasks only assigned to
known threads, let's move that runqueue to each of these threads. The
goal will be to arrange an N*(N-1) mesh instead of a central contention
point.
The global_rqueue_ticks had to be dropped (for good) since we'll now
use the per-thread rqueue_ticks counter for both trees.
A few points to note:
- the rq_lock stlil remains the global one for now so there should not
be any gain in doing this, but should this trigger any regression, it
is important to detect whether it's related to the lock or to the tree.
- there's no more reason for using the scope-based version of the ebtree
now, we could switch back to the regular eb32_tree.
- it's worth checking if we still need TASK_GLOBAL (probably only to
delete a task in one's own shared queue maybe).
The runqueue ticks counter is per-thread and wasn't initially meant to
be shared. We'll soon have to share it so let's make it atomic. It's
only updated when waking up a task, and no performance difference was
observed. It was moved in the thread_ctx struct so that it doesn't
pollute the local cache line when it's later updated by other threads.
Each thread has its own local thread id and its own global thread id,
in addition to the masks corresponding to each. Once the global thread
ID can go beyond 64 it will not be possible to have a global thread Id
bit anymore, so better start to remove it and use only the local one
from the struct thread_info.
Instead of having a global mask of all the profiled threads, let's have
one flag per thread in each thread's flags. They are never accessed more
than one at a time an are better located inside the threads' contexts for
both performance and scalability.
Like previous patches, this replaces the build-time code paths that were
conditionned by CONFIG_HAP_POOLS with runtime paths conditionned by
!POOL_DBG_NO_CACHE. One trivial test had to be added in the hot path in
__pool_alloc() to refrain from calling pool_get_from_cache(), and another
one in __pool_free() to avoid calling pool_put_to_cache().
All cache-specific functions were instrumented with a BUG_ON() to make
sure we never call them with cache disabled. Additionally the cache[]
array was not initialized (remains NULL) so that we can later drop it
if not needed. It's particularly huge and should be turned to dynamic
with a pointer to a per-thread area where all the objects are located.
This will solve the memory usage issue and will improve locality, or
even help better deal with NUMA machines once each thread uses its own
arena.
This will be a convenient way to communicate the thread ID and its
local ID in the group, as well as their respective bits when creating
the threads or when only a pointer is given.
This will ease the reporting of the current thread group ID when coming
from the thread itself, especially since it returns the visible ID,
starting at 1.
This registers a mapping of threads to groups by enumerating for each thread
what group it belongs to, and marking the group as assigned. It takes care of
checking for redefinitions, overlaps, and holes. It supports both individual
numbers and ranges. The thread group is referenced from the thread config.
This creates a struct tgroup_info which knows the thread ID of the first
thread in a group, and the number of threads in it. For now there's only
one thread group supported in the configuration, but it may be forced to
other values for development purposes by defining MAX_TGROUPS, and it's
enabled even when threads are disabled and will need to remain accessible
during boot to keep a simple enough internal API.
For the purpose of easing the configurations which do not specify a thread
group, we're starting group numbering at 1 so that thread group 0 can be
"undefined" (i.e. for "bind" lines or when binding tasks).
The goal will be to later move there some global items that must be
made per-group.
We want to make sure that the current thread_info accessed via "ti" will
remain constant, so that we don't accidentally place new variable parts
there and so that the compiler knows that info retrieved from there is
not expected to have changed between two function calls.
Only a few init locations had to be adjusted to use the array and the
rest is unaffected.
The last 3 fields were 3 list heads that are per-thread, and which are:
- the pool's LRU head
- the buffer_wq
- the streams list head
Moving them into thread_ctx completes the removal of dynamic elements
from the struct thread_info. Now all these dynamic elements are packed
together at a single place for a thread.
The TI_FL_STUCK flag is manipulated by the watchdog and scheduler
and describes the apparent life/death of a thread so it changes
all the time and it makes sense to move it to the thread's context
for an active thread.
The "thread_info" name was initially chosen to store all info about
threads but since we now have a separate per-thread context, there is
no point keeping some of its elements in the thread_info struct.
As such, this patch moves prev_cpu_time, prev_mono_time and idle_pct to
thread_ctx, into the thread context, with the scheduler parts. Instead
of accessing them via "ti->" we now access them via "th_ctx->", which
makes more sense as they're totally dynamic, and will be required for
future evolutions. There's no room problem for now, the structure still
has 84 bytes available at the end.
The scheduler contains a lot of stuff that is thread-local and not
exclusively tied to the scheduler. Other parts (namely thread_info)
contain similar thread-local context that ought to be merged with
it but that is even less related to the scheduler. However moving
more data into this structure isn't possible since task.h is high
level and cannot be included everywhere (e.g. activity) without
causing include loops.
In the end, it appears that the task_per_thread represents most of
the per-thread context defined with generic types and should simply
move to tinfo.h so that everyone can use them.
The struct was renamed to thread_ctx and the variable "sched" was
renamed to "th_ctx". "sched" used to be initialized manually from
run_thread_poll_loop(), now it's initialized by ha_set_tid() just
like ti, tid, tid_bit.
The memset() in init_task() was removed in favor of a bss initialization
of the array, so that other subsystems can put their stuff in this array.
Since the tasklet array has TL_CLASSES elements, the TL_* definitions
was moved there as well, but it's not a problem.
The vast majority of the change in this patch is caused by the
renaming of the structures.
The watchdog timer had no more reason for being shared with the struct
thread_info since the watchdog is the only user now. Let's remove it
from the struct and move it to a static array in wdt.c. This removes
some ifdefs and the need for the ugly mapping to empty_t that might be
subject to a cast to a long when compared to TIMER_INVALID. Now timer_t
is not known outside of wdt.c and clock.c anymore.
This removes the knowledge of clockid_t from anywhere but clock.c, thus
eliminating a source of includes burden. The unused clock_id field was
removed from thread_info, and the definition setting of clockid_t was
removed from compat.h. The most visible change is that the function
now_cpu_time_thread() now takes the thread number instead of a tinfo
pointer.
This removes the thread identifiers from struct thread_info and moves
them only in static array in thread.c since it's now the only file that
needs to touch it. It's also the only file that needs to include
pthread.h, beyond haproxy.c which needs it to start the poll loop. As
a result, much less system includes are needed and the LoC reduced by
around 3%.
