sysbench runs give different result for mysql database performance evaluation

i am trying to evaluate the performance of mysql database cluster , INNODB cluster (group replication) , so i use sysbench , i run multiple test using the lua scripts (read_write.lua / read_only.lua / bulk_insert.lua) , each test is run 100 runs for repetition (to give more accurate value) ,and took the mean of the result for each test with different number of threads, but i have a problem if i rerun the test on same servers with same sysbench variables and same values for mysql cluster configuration i have different result which make me confused , could any one advise of what could the problem please. noting that i am using 3 servers vms (on same datacenter vms ) with same specification for cluster , and one server as router on same vm , sysbench installed on different server also on same vm to not have network issues.

servers specification of cluster:

ram: 8G

cpu: 2cores , x86_64, 2593.906 MHz

sysbench version : 1.0.18-1

mysql version : 8.0.18

noting below is the same values on 3 servers of my.cnf file, for sure with different server id

my.cnf file on the 3 nodes:

sysbench command used for bulk insert

sysbench –mysql-host=router_IP –mysql-port=6446 –db-driver=mysql –mysql-user=root –mysql-password=** –mysql-db=test_cluster –threads=30 –events=100000 –time=60 /usr/share/sysbench/bulk_insert.lua run |cat > innodb.log

sysbench command used for read_only test

sysbench –mysql-host=router_IP –mysql-port=6447 –db-driver=mysql –mysql-user=root –mysql-password=** –mysql-db=test_cluster –tables=5 –table_size=2000000 –threads=30 /usr/share/sysbench/oltp_read_write.lua run |cat > innodb.log

RAW and/or rules as interpreted, can a Glamour Bard use the Enthralling Performance ability while casting Motivational Speech?

Can the following two mechanics work together or are they mutually exclusive or require something else? I am the DM and both the player at my table and me don’t agree or understand if it’s possible to utilize Enthralling Performance in conjunction with the spell motivational speech.

Enthralling Performance (Glamour Bard ability)

Starting at 3rd level, you can charge your performance with seductive, fey magic.

If you perform for at least 1 minute, you can attempt to inspire wonder in your audience by singing, reciting a poem, or dancing. At the end of the performance, choose a number of humanoids within 60 feet of you who watched and listened to all of it, up to a number equal to your Charisma modifier (minimum of one). Each target must succeed on a Wisdom saving throw against your spell save DC or be charmed by you. While charmed in this way, the target idolizes you, it speaks glowingly of you to anyone who speaks to it, and it hinders anyone who opposes you, avoiding violence unless it was already inclined to fight on your behalf. This effect ends on a target after 1 hour, if it takes any damage, if you attack it, or if it witnesses you attacking or damaging any of its allies.

If a target succeeds on its saving throw, the target has no hint that you tried to charm it.

Once you use this feature, you can’t use it again until you finish a short or long rest.

Motivational Speech (Acquistions Incorporated, p.77)

3rd-level enchantment
Casting Time: 1 minute
Range: 60 feet
Components: V
Duration: 1 hour

You address allies, staff, or innocent bystanders to exhort and inspire them to greatness, whether they have anything to get excited about or not. Choose up to five creatures within range that can hear you. For the duration, each affected creature gains 5 temporary hit points and has advantage on Wisdom saving throws. If an affected creature is hit by an attack, it has advantage on the next attack roll it makes. Once an affected creature loses the temporary hit points granted by this spell, the spell ends for that creature.

At Higher Levels. At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the temporary hit points increase by 5 for each slot level above 3rd.

Is it normal that the service WMI Performance Adapter always starts when launching Chrome browser? Whats the reason

Is it normal that the service WMI Performance Adapter (WmiApSrv.exe) always starts when launching Chrome browser? Whats the reason?

I have heared this service can be maliciously used to “communicate” through the internet via open ports?

When I forcefull end this process in the taskmanager, Chrome keeps running perfectly, without issues.

Could it be that this WMI process is needed because one of Chrome’s features called “Conceal local IP addresses with mDNS hostnames”?

Thanks!

Dynamic programming algorithm with an O(n) performance that will give the optimal solution

I am currently learning the dynamic substructure and optimal solution for the coin change-making, and one of the questions given from my teacher is to describe an overall O(n) dynamic programming algorithm that will give the optimal solution and why is it O(n)? Can anyone help me to understand the question? Thank you!

Slow performance of embedding Mathematica Demonstrations in webpages

When I embed a Mathematica Demonstration in my webpage, the performance is very slow and laggy.

For instance, if I follow the instruction video and embed the Radial Engine Demonstration in an HTML page, it takes about 5 seconds to load (that’s ok) and when I drag a slider, it takes about 2 seconds for the image to update (that’s a big problem). This is the case even for simpler demonstrations, such as this magnetic field demonstration.

Is there any way to improve performance?

When does setting the SORT_IN_TEMPDB option actually improve performance?

My question is related to index rebuilding, mainly the SORT_IN_TEMPDB option.

BOL states that:

Even if other users are using the database and accessing separate disk addresses, the overall pattern of reads and writes are more efficient when SORT_IN_TEMPDB is specified than when it is not.

On the other hand, one of the users states:

When rebuilding an index you would need twice the space of the index + 20% for the sorting. So in general to rebuild every index in your db you only need 120% of your biggest index in your DB. If you use SORT_IN_TEMPDB, you only win 20%, you still need an aditional 100% in your data file. Further more, using sort in tempdb increases your IO load drastically, since instead of Writing the index one time to the datafile, you now write it one time to the tempdb and then write it to the data file. So that is not always ideal.

Would you like to share your own experience about this option? Have you ever had to use this option while rebuilding indexes? What was the performance result?

Fstrim ruins bcache’s performance

Since Ubuntu 18.04 two machines I use, one desktop and one notebook, both started to present an occasional really slow boot and a really slow performance for everything after that boot. Both use a small SSD and a bigger HD through bcache.

Except for those occasions, they are fast. No noticeable difference from other PCs with SSD only. Bcache is great. And usually a reboot after that slow boot makes things go back to normal. That’s why I took so long to investigate it deeper.

Following instructions I probably found here in askubuntu, I used systemd-analyze to discover fstrim was causing it.

$   sudo systemd-analyze blame 2min 9.448s fstrim.service ... 

The package was found using this:

$   dpkg -S fstrim util-linux: /sbin/fstrim util-linux: /usr/share/man/man8/fstrim.8.gz util-linux: /lib/systemd/system/fstrim.service util-linux: /lib/systemd/system/fstrim.timer util-linux: /usr/share/bash-completion/completions/fstrim 

My guess is that this fstrim ruins bcache’s performance. It is scheduled for running once a week, which is consistent with the observed behaviour. It probably thinks the bcache device is a huge SSD and does its thing making the boot super slow, which also messes with the cache and thus every access after that is a cache miss.

It’s kind of fixed on my machines, since I disabled fstrim and it’s timer following the instructions here and the slow boot haven’t occurred again.

rm /var/lib/systemd/timers/stamp-fstrim.timer systemctl stop fstrim.service fstrim.timer systemctl disable fstrim.service fstrim.timer systemctl mask fstrim.service fstrim.timer 

But there’s probably better solutions to this. For example: there should be a way to disable fstrim for only one partition editing fstab.
There is, maybe… I have just found it reading ArchLinux’s wiki and a link to kernel.org from there. You just add nodiscard to the line of that bcache filesystem in fstab. I haven’t tested it yet. In my case it would be:

... # /home was on /dev/bcache0 during installation UUID=0880deae-1eeb-4c07-af01-a3db9d2d6282 /home           ext4    defaults,nodiscard        0       2 ... 

Even better would be bcache to report as not having trim support to lsblk --discard or fstrim to recognize a bcache partition and avoid it.

Any suggestions? Should I file a bug? Where?

Would forcing a lawyer to turn on their client with a Glamour Bard’s Enthralling Performance feature be seen as an attack?

Say you are a bard, level 3+. You have are being sued by an enemy, and you have got their lawyer tied up in a chair. You make them charmed after their failed saving throw against your Enthralling Performance feature, which states:

Each target must succeed on a Wisdom saving throw against your spell save DC or be charmed by you. While charmed in this way, the target idolizes you, it speaks glowingly of you to anyone who speaks to it, and it hinders anyone who opposes you, avoiding violence unless it was already inclined to fight on your behalf. This effect ends on a target after 1 hour, if it takes any damage, if you attack it, or if it witnesses you attacking or damaging any of its allies.

Would charming the lawyer and making him throw out the case be seen as an attack against the lawyer’s ally, your enemy?