In the virtualization scenario, you can use pvipi to optimize the sending of
IPI interrupts and reduce the number of vmexit.
rps_using_pvipi test
Test guest: 32 core, 64G memory, virtio-net 8 queues, rss interrupt is bound
to 24-31 core. Observe the number of vmexit of 31 cores.
1. 1000000pps
100 iperf instances, 10000pps per instance.
disable rps_using_pvipi 68077 vmexit/s
enable rps_using_pvipi 21138 vmexit/s
2. 2000000pps
1000 iperf instances, 2000pps per instance.
disable rps_using_pvipi 40879 vmexit/s
enable rps_using_pvipi 9195 vmexit/s
3. 2000000pps
2000 iperf instances, 1000pps per instance.
disable rps_using_pvipi 24746 vmexit/s
enable rps_using_pvipi 7292 vmexit/s
Enabling rps_using_pvipi can greatly reduce the number of vmexit.
Signed-off-by: yongduan <yongduan@tencent.com>
Run an asynchronous function on a many cpus.
smp_call_function_many_async_begin
for_each_csd
smp_call_function_many_async
smp_call_function_many_async_end
Signed-off-by: yongduan <yongduan@tencent.com>
Without preemption, if syscall excutes too long it will significantly
affect performance of other important processes. So add a shceduling
point when showing root memcg usage.
Signed-off-by: yongduan <yongduan@tencent.com>
Signed-off-by: charliecgxu <charliecgxu@tencent.com>
This commit add cpu.offline to cpu cgroup, echo 1 > cpu.offline would
convert all tasks under this cgroup to offline task. Beside, a new
sysctl sysctl_sched_bt_ignore_cpubind is added, which makes offline
tasks ignoring CPU binding and running on any CPU.
Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
Signed-off-by: Hua Liu <shookliu@tencent.com>
Signed-off-by: Xiaogguang Chen <xiaoggchen@tencent.com>
Signed-off-by: Zhiguang Peng <zgpeng@tencent.com>
Signed-off-by: Bin Fan <tombinfan@tencent.com>
Signed-off-by: He Chen <heddchen@tencent.com>
Also a switch had been added to control whether show the
subtree or not.
Signed-off-by: Chen He <heddchen@tencent.com>
Signed-off-by: Peng Zhiguang <zgpeng@tencent.com>
Signed-off-by: Chen Xiaoguang <xiaoggchen@tencent.com>
Offline tasks (BT tasks) may have some performance impact to online
tasks.
In this commit, we introduce Intel RDT features to limit offline tasks
L3 cache usage to avoid the influence caused by offline tasks.
Signed-off-by: Xiaoguang Chen <xiaoggchen@tencent.com>
Signed-off-by: He Chen <heddchen@tencent.com>
since we disable clocksource switch when tsc not stable, we need a
counter to track tsc unstable did happend.
Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
output more information when clocksource got unstable,
and add kernel.clocksource_switch_unstable_cs to control
whether to switch off unstable clocksource.
Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
use lightweight track method to count free objects in
slub, remove heavy logic in spin_lock_irqsave.
Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
Commit:
de53fd7aedb1 ("sched/fair: Fix low cpu usage with high throttling by removing expiration of cpu-local slices")
introduced a few compilation warnings:
kernel/sched/fair.c: In function '__refill_cfs_bandwidth_runtime':
kernel/sched/fair.c:4365:6: warning: variable 'now' set but not used [-Wunused-but-set-variable]
kernel/sched/fair.c: In function 'start_cfs_bandwidth':
kernel/sched/fair.c:4992:6: warning: variable 'overrun' set but not used [-Wunused-but-set-variable]
Also, __refill_cfs_bandwidth_runtime() does no longer update the
expiration time, so fix the comments accordingly.
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Reviewed-by: Dave Chiluk <chiluk+linux@indeed.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pauld@redhat.com
Fixes: de53fd7aedb1 ("sched/fair: Fix low cpu usage with high throttling by removing expiration of cpu-local slices")
Link: https://lkml.kernel.org/r/1566326455-8038-1-git-send-email-cai@lca.pw
Signed-off-by: Ingo Molnar <mingo@kernel.org>
It has been observed, that highly-threaded, non-cpu-bound applications
running under cpu.cfs_quota_us constraints can hit a high percentage of
periods throttled while simultaneously not consuming the allocated
amount of quota. This use case is typical of user-interactive non-cpu
bound applications, such as those running in kubernetes or mesos when
run on multiple cpu cores.
This has been root caused to cpu-local run queue being allocated per cpu
bandwidth slices, and then not fully using that slice within the period.
At which point the slice and quota expires. This expiration of unused
slice results in applications not being able to utilize the quota for
which they are allocated.
The non-expiration of per-cpu slices was recently fixed by
'commit 512ac999d275 ("sched/fair: Fix bandwidth timer clock drift
condition")'. Prior to that it appears that this had been broken since
at least 'commit 51f2176d74ac ("sched/fair: Fix unlocked reads of some
cfs_b->quota/period")' which was introduced in v3.16-rc1 in 2014. That
added the following conditional which resulted in slices never being
expired.
if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
/* extend local deadline, drift is bounded above by 2 ticks */
cfs_rq->runtime_expires += TICK_NSEC;
Because this was broken for nearly 5 years, and has recently been fixed
and is now being noticed by many users running kubernetes
(https://github.com/kubernetes/kubernetes/issues/67577) it is my opinion
that the mechanisms around expiring runtime should be removed
altogether.
This allows quota already allocated to per-cpu run-queues to live longer
than the period boundary. This allows threads on runqueues that do not
use much CPU to continue to use their remaining slice over a longer
period of time than cpu.cfs_period_us. However, this helps prevent the
above condition of hitting throttling while also not fully utilizing
your cpu quota.
This theoretically allows a machine to use slightly more than its
allotted quota in some periods. This overflow would be bounded by the
remaining quota left on each per-cpu runqueueu. This is typically no
more than min_cfs_rq_runtime=1ms per cpu. For CPU bound tasks this will
change nothing, as they should theoretically fully utilize all of their
quota in each period. For user-interactive tasks as described above this
provides a much better user/application experience as their cpu
utilization will more closely match the amount they requested when they
hit throttling. This means that cpu limits no longer strictly apply per
period for non-cpu bound applications, but that they are still accurate
over longer timeframes.
This greatly improves performance of high-thread-count, non-cpu bound
applications with low cfs_quota_us allocation on high-core-count
machines. In the case of an artificial testcase (10ms/100ms of quota on
80 CPU machine), this commit resulted in almost 30x performance
improvement, while still maintaining correct cpu quota restrictions.
That testcase is available at https://github.com/indeedeng/fibtest.
Fixes: 512ac999d275 ("sched/fair: Fix bandwidth timer clock drift condition")
Signed-off-by: Dave Chiluk <chiluk+linux@indeed.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: John Hammond <jhammond@indeed.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kyle Anderson <kwa@yelp.com>
Cc: Gabriel Munos <gmunoz@netflix.com>
Cc: Peter Oskolkov <posk@posk.io>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Brendan Gregg <bgregg@netflix.com>
Link: https://lkml.kernel.org/r/1563900266-19734-2-git-send-email-chiluk+linux@indeed.com
Add the max_map_count isolation switch kernel.isolate_max_map_count;
The isolation of max_map_count is turned on by default. If you want
to turn it off, set kernel.isolate_max_map_count to 0;
Signed-off-by: Zhiguang Peng <zgpeng@tencent.com>
The offline scheduler named BT sched is based on the CFS scheduler. We
also use the rb-tree as the run queue to save the runnable tasks. And the
vruntime concept is also used in the offline scheduler. And the priority
of offline scheduler is from 140 to 179. So now the schedulers in the
kernel are as follows: stop, RT, CFS, BT and idle.
Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
Signed-off-by: Hua Liu <shookliu@tencent.com>
Signed-off-by: Xiaogguang Chen <xiaoggchen@tencent.com>
Signed-off-by: Zhiguang Peng <zgpeng@tencent.com>
Signed-off-by: Bin Fan <tombinfan@tencent.com>
Signed-off-by: He Chen <heddchen@tencent.com>
epoll hrtimer patch may increase loop times if timeout set to 1ms.
This patch add new sysctl control the minimal wait time, and default
to 1 jiffies.
Signed-off-by: Samuel Liao <samuelliao@tencent.com>
Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
Signed-off-by: Fuhai Wang <fuhaiwang@tencent.com>
yongduan