xinyiZzz commented on code in PR #9250:
URL: https://github.com/apache/incubator-doris/pull/9250#discussion_r859755912
##########
be/src/vec/common/allocator.h:
##########
@@ -146,8 +146,13 @@ class Allocator {
std::to_string(old_size) + " to " +
std::to_string(new_size) + ".",
doris::TStatusCode::VEC_CANNOT_MREMAP);
-
/// No need for zero-fill, because mmap guarantees it.
+
+ if constexpr (mmap_populate)
+ // MAP_POPULATE seems have no effect for mremap as for mmap,
+ // Zero-fill enlarged memory range explicitly to pre-fault the
pages
+ if (new_size > old_size)
+ memset(reinterpret_cast<char*>(buf) + old_size, 0,
new_size - old_size);
Review Comment:
Why manual zero-fill is needed here,
CK's comment mentions that mmap is automatically zero-filled. The manual
also seems to say so: https://linux.die.net/man/2/mmap
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