Cpu Spiking For No Reason

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Perry Dearmas

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Dec 8, 2023, 9:39:28 AM12/8/23
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The graph above shows the constant CPU spiking over the course of a week. This issue was causing latency across our entire app. And the strange thing was, these CPU spikes did not correspond with any increase in traffic, or anything else for that matter.

At first, I thought maybe Redis was doing a lot of memory swapping, which is a common culprit to a badly performing Redis server. Running the "INFO" command ( ) using the redis-cli, I saw that we did not even exhaust half the available memory, so the spikes can't be due to memory swapping. But something else did catch my eye. We had a ton of keys, especially a lot without a TTL (time to live), that will be sticking around forever, for no reason, if we didn't do something about them. Investigating the code, I found the key pattern needed for me to identify the, at least the most obvious, keys that served no more purpose. I updated the code to add a TTL to these types of keys, then...

cpu spiking for no reason


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If the Sqlservr.exe process is causing high CPU usage, by far, the most common reason is SQL Server queries that perform table or index scans, followed by sort, hash operations and loops (nested loop operator or WHILE (T-SQL)). To get an idea of how much CPU the queries are currently using, out of overall CPU capacity, run the following statement:

thanks for the response. At the time I wrote the above message, I didn't HAVE a Case ID because I was unable to contact support either by phone or through the portal (I STILL can't use the support portal for some inane reason). it seems it's now been assigned 04437859.

ive been staring at the resource monitor for 2 days now trying to figure out wtf is going on.. its only ever avast that spikes up to crazy high usage.. normal its at less than one percent usage but it will spike up to osmetimes 80-90% cpu usage for no reason at all. extremely annoying.

you think i complete revo uninstall and a reinstall will fix it? or is avast just bugged now after an update or something?

yeah that sounds great, ill definitely love to add that to my list of awesome useful software..

and the main reason i like having an antivirus is because once in a while ill torrent movies or music or programs and i feel its just better to be safe than sorry. It has helped me a handful of times in my life. Ive actually never used JUST the windows stock antivirus. ive always heard bad things about it. Like its not thorough enough in the real time protection department. Id be interested to see stats on it vs other av programs.

im about to hop ion the car. when i get back ill check this thread for that link. Thank you for that! ive ran into the not having permissions issue many times and its always irritating as hell!

Anybody have any ideas what could be happening? Most postings point to possible heavy queries, but I'd expect to see CPU % climbing not instantly spiking like that. In addition, it's the exact same test, the exact same queries, the exact same database. Yet on SQL 2008 fine, on 2012, we get the spike. We can see that the system is overloaded with SOS_SCHEDULER_YIELD locks, but all I've read just says "That means you're CPU bound." One posting suggested spinlocks, and I found we are way high on SOS_CACHESTORE_CLOCK spinlocks, but we're not really sure if that has any meaning at all.

Instant spiking like that screams that we've hit some sort of threshold, but we can't figure out what it could possibly be. Any thoughts about what could be happening? Again -- same tests, same machine, same queries, same data on SQL 2008 are great. On SQL 2012 runs great and then spikes from 10% CPU usage to 100% CPU use instantly, over the course of a couple of seconds.

The second point, I have no reason to doubt you. I just don't have any systems that push the limits of the hardware quite so close (not sure if that makes me lucky, or not in this case). I can certainly understand the CPU numbers getting skewed by the generation of extra query plans, but I can't grasp how the reads may get affected. In any case, if I were the OP, I would be looking for differences in orders of magnitude (I still suspect bad query plans are at the root here).

I have a Clearpass hardware appliance that's consistently (CPU) spiking every 5 minutes. This is a system that is not in production and only in test, so I'm at a loss to explain the spike. It'll go from 3% to 20%, then drop right back down. Is there a process that kicks off every 5 minutes that would explain this? I have checked under System Monitor > Process Monitor, and none of the processes in the drop down are spiking.

However, there are internal processing events that can cause the CPU to jump. There's also situations where, for some reason, the special hardware that normally handles transit traffic sends that traffic to the CPU for processing.

Been a long time Intel shop and we are going through another lifecycle replacement of our servers. We have been working with Dell to test out a pair of R6525's running the AMD Milan EPYC 7543 32-Core procs. We loaded them with ESXi 7.02 (and recently applied the latest 7.02a update). We have a large 48 node Intel based cluster with several hundred RDP VMs that participate in a load balance pool so the workload is identical. We moved some of these VM's onto a dedicated 2 node EPYC cluster and initially things looked good, until we started having machine check error crashes that just rebooted the host, no PSOD. VMware recommended a driver update based on something they saw in the logs. Since doing that, we have not had any more of them. But what we did notice is that both EPYC hosts randomly hit 99% CPU usage for varying amounts of time. With no VM's running on one of these hosts, CPU is quiet. You move just 1 VM onto it, and spiking occurs. There is not enough CPU allocated to 1 VM to cause the host to spike like this so i can rule out anything having to do with activity going on inside the guest OS.

Hey guys, a little update. I'm working in Logic X right now and everything was going fine, then all of a sudden the CPU starting spiking like crazy again. So I decided to do some detective work. I opened up activity monitor and nothing was really sticking out like a sore thumb, so I just started closing programs. I closed Google Chrome, I closed f.lux, I closed iTunes, etc.

UPDATE: So here's a quick screen capture of me playing the piano with the high CPU / audio stutter issue, and then look what happens when I turn off Wi-fi. BOOM. Problem solved. Any reason why the wi-fi may be the culprit?

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