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linuxmemorysisense

Application fails when free memory is low but available memory is high

I am building data models via an app called Sisense on Linux. Lately the process fails with an out of memory error. Running free -h I see that that the failure occurs when free memory is low, but before it actually reaches zero and even though there is still plenty of available memory.

Here is the exception:

Failed to build custom table: Rule_pre; BE#521691 SQL error: SafeModeException:
Safe-Mode triggered due to memory pressure. Pod physical memory: 5.31 GB available, 2.87 GB 
used, 8.19 GB total. Server physical memory: 4.86 GB available, 28.67 GB used, 
33.54 GB total. Application total virtual memory: 2.54 GB. The server exceeded 85% capacity 
(28.67/33.54). Possible ways to reduce memory pressure: increase server memory, adjust data 
modelling (M2M, un-indexed string fields, etc.), reduce number of simultaneous queries

And here is the output of free -h where you can see the declining memory in the center "free" column. Once free memory got below 235 MB I saw the above exception.

Here is the memory usage per the linux util "free"

The free util man page has these definitions for free and available memory:

free Unused memory (MemFree and SwapFree in /proc/meminfo)

available Estimation of how much memory is available for starting new applications, without swapping. Unlike the data provided by the cache or free fields, this field takes into account page cache and also that not all reclaimable memory slabs will be reclaimed due to items being in use (MemAvailable in /proc/meminfo, available on kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as free

As I read on the internet there seems to be a casualness about low free memory. That it is not an issue. But the failure coincides with free memory getting to low. If I understand the man page, the available memory is for starting new applications. I am assuming then that available memory is not available to the existing application that fails, and that free memory is indeed what matters. But any confirmation form others or additional explanation would be appreciated. I'd also be curious about opinions on whether this may constitute a memory leak or if I should simply allocate more memory somehow perhaps at the Linux layer.

Solution

  • I think I have enough understanding here. Free memory never goes below 200MB whether a build fails or succeed. It does not appear to be an indicator of the issue. A successful build will also show a drop in free memory to 200MB.