Rare bug in memory pool where allocation can finish on superblock in empty state #452
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Broken / incorrect code; it could be Kokkos' responsibility, or others’ (e.g., Trilinos)
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gmackey
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Requires significant redesign to catch corner-cases. |
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Tonight there was a segmentation fault on openmp.task_fib on kokko-develop in addition to the always failing cuda.task_fib on Pascal. |
hcedwar
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Apr 18, 2017
To be used in MemoryPool for TaskDAG maturing issue kokkos#320 . Designed to help address issue kokkos#452 .
hcedwar
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Apr 18, 2017
race conditions by condensing state representation to a single integer and simplifying algorithm. Addresses issues kokkos#320 , kokkos#487 , kokkos#452 Using power-of-two Kokkos::Impl::concurrent_bitset size to streamline implementation and align with MemoryPool needs. Unit testing over a range of superblocks the following sequence: 1) allocate N of varying size 2) deallocate N/3 of these 3) reallocation deallocated 4) concurrently deallocate and allocate N/3 of these
hcedwar
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Apr 19, 2017
race conditions by condensing state representation to a single integer and simplifying algorithm. Addresses issues kokkos#320 , kokkos#487 , kokkos#452 Using power-of-two Kokkos::Impl::concurrent_bitset size to streamline implementation and align with MemoryPool needs. Unit testing over a range of superblocks the following sequence: 1) allocate N of varying size 2) deallocate N/3 of these 3) reallocation deallocated 4) concurrently deallocate and allocate N/3 of these Add performance test for memory pool. Add performance enhancement note for multiple hints per block size.
hcedwar
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Apr 19, 2017
race conditions by condensing state representation to a single integer and simplifying algorithm. Addresses issues kokkos#320 , kokkos#487 , kokkos#452 Using power-of-two Kokkos::Impl::concurrent_bitset size to streamline implementation and align with MemoryPool needs. Unit testing over a range of superblocks the following sequence: 1) allocate N of varying size 2) deallocate N/3 of these 3) reallocation deallocated 4) concurrently deallocate and allocate N/3 of these Add performance test for memory pool. Add performance enhancement note for multiple hints per block size.
hcedwar
added a commit
to hcedwar/kokkos
that referenced
this issue
Apr 19, 2017
To be used in MemoryPool for TaskDAG maturing issue kokkos#320 . Designed to help address issue kokkos#452 .
hcedwar
added a commit
to hcedwar/kokkos
that referenced
this issue
Apr 19, 2017
race conditions by condensing state representation to a single integer and simplifying algorithm. Addresses issues kokkos#320 , kokkos#487 , kokkos#452 Using power-of-two Kokkos::Impl::concurrent_bitset size to streamline implementation and align with MemoryPool needs. Unit testing over a range of superblocks the following sequence: 1) allocate N of varying size 2) deallocate N/3 of these 3) reallocation deallocated 4) concurrently deallocate and allocate N/3 of these Add performance test for memory pool. Add performance enhancement note for multiple hints per block size.
hcedwar
added a commit
to hcedwar/kokkos
that referenced
this issue
Apr 19, 2017
race conditions by condensing state representation to a single integer and simplifying algorithm. Addresses issues kokkos#320 , kokkos#487 , kokkos#452 Creating power-of-two Kokkos::Impl::concurrent_bitset size to streamline implementation and align with MemoryPool needs. Unit testing over a range of superblocks the following sequence: 1) allocate N of varying size 2) deallocate N/3 of these 3) reallocation deallocated 4) concurrently deallocate and allocate N/3 of these Add performance test for memory pool. Add performance enhancement note for multiple hints per block size.
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The redesigned memory pool explicitly eliminates this situation. |
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In the memory pool, it is possible for an allocation to finish on a superblock in the empty state. Allocations can only start on superblocks in the active state, but it is possible for the superblock to transition to full, then partially full, then empty before the allocation completes. This is extremely unlikely and hasn't been encountered yet, but the issue needs to be addressed.
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