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slightly improve jemalloc allocator API header (#7592) 

Summary:
Fix a few typos and avoid a potential nullptr dereference.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7592

Reviewed By: zhichao-cao

Differential Revision: D24582111

Pulled By: riversand963

fbshipit-source-id: 51e9260e8cad1fcdedd310c889f0faeec6efd937
This commit is contained in:
jsteemann 2020-10-28 13:45:21 -07:00 committed by Facebook GitHub Bot
parent 248d10fb96
commit 2404f8b9ec
2 changed files with 15 additions and 15 deletions
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24
include/rocksdb/memory_allocator.h
View File

@ -45,31 +45,31 @@ struct JemallocAllocatorOptions {
bool limit_tcache_size = false;
// Lower bound of allocation size to use tcache, if limit_tcache_size=true.
// When used with block cache, it is recommneded to set it to block_size/4.
// When used with block cache, it is recommended to set it to block_size/4.
size_t tcache_size_lower_bound = 1024;
// Upper bound of allocation size to use tcache, if limit_tcache_size=true.
// When used with block cache, it is recommneded to set it to block_size.
// When used with block cache, it is recommended to set it to block_size.
size_t tcache_size_upper_bound = 16 * 1024;
};
// Generate memory allocators which allocates through Jemalloc and utilize
// MADV_DONTDUMP through madvice to exclude cache items from core dump.
// Generate memory allocator which allocates through Jemalloc and utilize
// MADV_DONTDUMP through madvise to exclude cache items from core dump.
// Applications can use the allocator with block cache to exclude block cache
// usage from core dump.
//
// Implementation details:
// The JemallocNodumpAllocator creates a delicated jemalloc arena, and all
// allocations of the JemallocNodumpAllocator is through the same arena.
// The memory allocator hooks memory allocation of the arena, and call
// madvice() with MADV_DONTDUMP flag to exclude the piece of memory from
// core dump. Side benefit of using single arena would be reduce of jemalloc
// metadata for some workload.
// The JemallocNodumpAllocator creates a dedicated jemalloc arena, and all
// allocations of the JemallocNodumpAllocator are through the same arena.
// The memory allocator hooks memory allocation of the arena, and calls
// madvise() with MADV_DONTDUMP flag to exclude the piece of memory from
// core dump. Side benefit of using single arena would be reduction of jemalloc
// metadata for some workloads.
//
// To mitigate mutex contention for using one single arena, jemalloc tcache
// (thread-local cache) is enabled to cache unused allocations for future use.
// The tcache normally incur 0.5M extra memory usage per-thread. The usage
// can be reduce by limitting allocation sizes to cache.
// The tcache normally incurs 0.5M extra memory usage per-thread. The usage
// can be reduced by limiting allocation sizes to cache.
extern Status NewJemallocNodumpAllocator(
JemallocAllocatorOptions& options,
std::shared_ptr<MemoryAllocator>* memory_allocator);

6
memory/jemalloc_nodump_allocator.cc
View File

@ -132,6 +132,9 @@ size_t JemallocNodumpAllocator::UsableSize(void* p,
Status NewJemallocNodumpAllocator(
JemallocAllocatorOptions& options,
std::shared_ptr<MemoryAllocator>* memory_allocator) {
if (memory_allocator == nullptr) {
return Status::InvalidArgument("memory_allocator must be non-null.");
}
*memory_allocator = nullptr;
Status unsupported = Status::NotSupported(
"JemallocNodumpAllocator only available with jemalloc version >= 5 "
@ -143,9 +146,6 @@ Status NewJemallocNodumpAllocator(
if (!HasJemalloc()) {
return unsupported;
}
if (memory_allocator == nullptr) {
return Status::InvalidArgument("memory_allocator must be non-null.");
}
if (options.limit_tcache_size &&
options.tcache_size_lower_bound >= options.tcache_size_upper_bound) {
return Status::InvalidArgument(