[WPE 2.38] Possible memory leak or GC not working

[gnulux]

Hi [Recipient Name],

I am currently running cog 0.12.3 with Webkit 2.38.6 on an IMX8plus ​ARM64 Yocto embedded system, displaying a JavaScript page generated from ReactJS.

A few months ago, I updated my Yocto meta-webkit to use WebPlatformForEmbedded/WPEWebKit wpe-2.38. I configured the following memory limitation variables:

WPE_POLL_MAX_MEMORY="databaseprocess:10m,networkprocess:5m,webprocess:140m,rpcprocess:10m"
WPE_RAM_SIZE="182m"

After restarting cog, the WPEWebProcess initially operates as expected, keeping memory usage below 180MB, and I can observe garbage collection (GC) reclaiming memory in the logs. However, if I leave my application open on COG for approximately seven days without any screen operations, I notice a continuous increase in WPEWebProcess memory consumption, as shown in the graph below. It appears that the GC stops functioning during this period.

Could you please advise on how I can effectively monitor what is causing this progressive memory growth?

[justinmichaud]

Does this just happen on your app? Or do you experience it on other sites too? Please also try disabling JIT, to see if you observe the same trend. You can do that by setting the environment variable JSC_useJIT=0. Confirm that your settings are working with JSC_validateOptions=1 JSC_invalidAndShouldCrash=1

[gnulux]

Hi ,
The issue seams to be related to my app but i didn't validate on another website or app .
Contrary to what I mentioned in my last update, the application is actively being used via the touchscreen when the leak occurs.
I have configured the following settings: JSC_useJIT=0, JSC_validateOptions=1, and JSC_invalidAndShouldCrash=1 and my application still works . I will provide an update on the trend in a few days.

[justinmichaud]

my application still works

This means the settings aren't being applied unfortunately, it should crash

[gnulux]

Hi,

You mean the process should crash at start ?
This is the command i pass on command line :
JSC_useJIT=0 JSC_validateOptions=1 JSC_invalidAndShouldCrash=1 COG_PLATFORM_WL_VIEW_FULLSCREEN=1 COG_URL=http://127.0.0.1:8080 /usr/bin/cog -P wl

The same command with JSC_logGC=1 , show GC output in journalctl -xf -u cog
And the application start normally

[justinmichaud]

I guess if logGC works, it is probably fine. Let's see if the memory usage changes

[gnulux]

Hi ,

Following the activation of JSC_useJIT=0 last Friday, we've observed a complete reversal in memory consumption. The current trend now shows a significant reduction in memory usage, as illustrated in the attached graph

[justinmichaud]

Fun! This is great, I know what your problem is: we just keep tiering up new jit code.

We have discussed adding API to turn off jitting after a while. There are tons of things that can be done about this, but it is a bit of ways off and requires some deep thought.

So for now: maybe try setting JSC_jitMemoryReservationSize to something small, and measure the memory/performance of your application?

It is also worth noting that since this is JIT code and you need the memory, you can always ask nicely for the vm to release it. If you compile with developer mode enabled and run with JSC_useDollarVM=1, you can run:

$vm.triggerMemoryPressure()

in your application code. This should reduce your memory usage, and if it doesn't, it is totally a bug that we need to fix.

*** Developer mode / dollarVM is very dangerous for production, it is just for testing ***

If that works, perhaps we need to make some memory pressure API.

[gnulux]

Understood , but i have several devices in production and i'm wondering if it is safe to only disable JIT ? or do i have to set JSC_jitMemoryReservationSize. Regarding my last tests it seems to work fine without JIT and consume less memory than before.

[justinmichaud]

If you are fine with the decreased performance, it is totally safe to disable JIT