Does anyone know what Tools->Profile->SPI mean?
It eats near 25-30% processors time of my RB2011UAS, v6.4
SPI is the LED touch-screen on the 2011 series.
please detail what is SPI on RB750 .. and RB450 and … RB493 … since I face same situation on my machines … strangely … when they have free memory under 4-7 MiB … rest is occupied by Web Proxy Cache.
SPI can stand for Serial Peripheral Interface, that would match to LCD/Touchscreen on the RB2011 or SDcard for units with an appropriate slot, maybe even for the system flash.
It may also be Statefull Packet Inspection…
You read my mind. when SPI eating CPU … I was looking on our Border Firewall for Attack Kind of Sessions. I found NONE. So in my experience SPI joust activate himself … without any exterior reason. I believe is something wrong in software, or something missing in software. (software means 5.6 or 6.5)
SPI basically means, that your firewall ACLs are statefull as compared to stateless. It’s the feature which allows you to have rules whith conditions like “established” or “related” and is needed for NAT. I think you confuse it with IPS intrusion prevention system, am I right?
Thank you for details. On our machines Firewall rules are non existent. we use firewall rule ONLY in case we want to block or filter someone. The only rules is NAT for Redirecting HTTP to local port 8080 acting as Web proxy (transparent proxy).
The machine generating most of the problems with Memory and Web proxy … have only Firewalls rules with DROP as action.
Well NAT requires SPI aka connection tracking. But until MT comments on what SPI really means, we both stumble in the dark. 
Your web proxy doesn’t use a microSD card for storage by any chance?
RB750, 450 and 493 do not have possibility for any external memory, not even USB.
Yesterday I was having problems again with the 493 .. I decide to disable the local cache from Web Proxy because again SPI and Unclassified takes 20-30 % of CPU and machine was slow responsive.
Strange thing is that WAN interface showed only a traffic of 15-20 mbps. so it seems the CPU of this machines was designed with NO CACHE in mind.
I never tried web caching on those systems as I was sure about the fact, that they are to weak for this anyway. 
I would recommend using a cheap x86 box with lots of ram for caching. RB750, 450 and 493 are in my oppinion not suitable for this task.
I perfectly agree with you. this equipment’s are installed in QUITE EXTREME REMOTE areas far from civilized world replacing x86 computers before. (because of the space and low power consumption requirements).
We will focus setting cache on none and using Proxy Cluster cache.
I’m gonna wake this topic because i’m facing SPI.
Does anyone one what is this “SPI”??
+1
This link is outdated: https://wiki.mikrotik.com/wiki/Manual:Tools/Profiler
We will contribute to keep you updated!
SPI stands for Serial Peripheral Interface. It is one of the buses on the router that is used to talk to certain components, like the LCD panel as previously stated. Anyone that has ever message with an Arduino should be familiar with this type of bus.
https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus
I was seeing 30% CPU utilization on a router today and all of the usage was on SPI. I went into the LCD configuration and changed it to “Read Only Mode” and the usage dropped down to 2-4% for SPI in the profile tool and now the router is sitting at ~8% CPU utilization with SPI only using 2-4% periodically, which makes sense because if that is the router updating the LCD screen and I am running the “stats slideshow” for the WAN interface on the LCD, so I would expect some CPU utilization there as it updates the graphs.
What about the stateful packet inspection?
I would think that would fall under the category of firewall as conntrack is a component of iptables.
Unfortunately I cant find any instance of where anyone from Mikrotik has officially documented what spi in the profile tool actually means. My comments are based purely on observed behavior of the platform.
My understanding is that all SOHO device in the current line of products (i.e. those with only 16MB of flash) also have Flash drive sitting on the SPI bus.
Like you, i disabled the option /lcd and voa lá my CPU is bellow then 10%. Thanks for explanation.
I have the same issue on RB1100AHx4 Dude Edition.
Tried to entirely disable firewall, SPI CPU usage remains unchanged and very high.
I wonder what peripheral is using that much resources, since there is no LCD on these devices. Any official comment from MT would indeed be very welcome…
Dude is installed on this machine, might it be access to the database on disk/flash memory?
I’ve experienced such an issue on my hap ac (962UiGS-5HacT2HnT) when I’ve set action “disk” for error,critical,warning and info logging topics (/system logging)
Since there are only 16MB total and ~7% free in most usage cases, internal flash was getting full when log files sizes grew.
There was 100% cpu usage (23% networking, 75% spi and minor %% of others). System didn’t have free space to write logs.
I’ve returned echo action to info and left disk action to others. Problem got solved.