I’m trying to valgrind a heisenbug on a process which uses more than 32 Gb of ram and hitting this valgrind limitation, is this an arbitrary one that could be avoided by recompiling valgrind or is it a hard one?
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I’m trying to valgrind a heisenbug on a process which uses more than 32 Gb of ram and hitting this valgrind limitation, is this an arbitrary one that could be avoided by recompiling valgrind or is it a hard one?
The limit is arbitrary and can be changed by recompiling valgrind.
Valgrind keeps track of memory using a 2-level sparse array. 16 bits of the address are used to index into a 65536-entry table containing a pointer to a second-level map, which tracks a range of the address space (normally 2¹⁶ bytes = 64KB for 32-bit processes, 2¹⁹ bytes = 512KB for 64-bit processes). So the total amount of memory that can be tracked by this 2-level sparse array is 65536 × this chunk size. By modifying the code, the size of these chunks can be increased to a larger power of 2, at the cost of using more memory to track most partial chunks.
In this message on the valgrind-users mailing list, Julian Seward explains how to increase the limit from 32GB to 128GB:
Update:
The maximum amount of memory that Valgrind can use has increased in recent versions: