Re: Heap is a lot larger than used, how to find the cause?

[nick_mospan]

My table has 54 columns of various simple types, mainly floats, symbols, ints and timestamps. Each column is of around 2Mb in size.

I can reproduce it with your code by dropping n to 2000000, which makes columns similar in size to my case. .Q.gc[] does not help releasing the excess heap to the OS:

 

q).Q.w[] 
used| 50694464 
heap| 134217728 
peak| 201326592 
wmax| 0 
mmap| 0 
mphy| 34359267328 
syms| 696 
symw| 37613

 

Each column with n:2000000 should be allocated 16777216 bytes of heap.

 

q)(-22!) each value flip position 
16000014 8667837 16000014

 

What is the reason for such behaviour? Are these columns small enough to lead to memory fragmentation or there’s something else going on?