pitrou commented on a change in pull request #12116:
URL: https://github.com/apache/arrow/pull/12116#discussion_r806108396
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File path: cpp/src/arrow/memory_pool.cc
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@@ -603,14 +643,109 @@ class BaseMemoryPoolImpl : public MemoryPool {
stats_.UpdateAllocatedBytes(-size);
}
- void ReleaseUnused() override { Allocator::ReleaseUnused(); }
+ protected:
+ virtual Status AllocateImmutableZeros(int64_t size, uint8_t** out) {
+#ifdef USE_MMAP_FOR_IMMUTABLE_ZEROS
+ if (size > 0) {
+ *out = static_cast<uint8_t*>(mmap(
+ nullptr, size, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS |
MAP_NORESERVE, -1, 0));
Review comment:
Ah, you're right, we don't know that the allocator returned us
zero-allocated memory, unfortunately.
(note that both jemalloc and mimalloc have zero-initializing allocation
APIs, so we could use those)
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