diff options
Diffstat (limited to 'erts/emulator/internal_doc/DelayedDealloc.md')
| -rw-r--r-- | erts/emulator/internal_doc/DelayedDealloc.md | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/erts/emulator/internal_doc/DelayedDealloc.md b/erts/emulator/internal_doc/DelayedDealloc.md index b7d87b839f..4b7c774141 100644 --- a/erts/emulator/internal_doc/DelayedDealloc.md +++ b/erts/emulator/internal_doc/DelayedDealloc.md @@ -19,7 +19,7 @@ the Erlang VM where memory allocation/deallocation is frequent and references to memory also are passed around between threads this solution will also scale poorly due to lock contention. -Functionality Used to Adress This problem +Functionality Used to Address This problem ----------------------------------------- In order to reduce contention due to locking of allocator instances we @@ -44,12 +44,12 @@ deallocation. The "message box" is implemented using a lock free single linked list through the memory blocks to deallocate. The order of the elements in this list is not important. Insertion of new free blocks will be made -somewhere near the end of this list. Requirering that the new blocks +somewhere near the end of this list. Requiring that the new blocks need to be inserted at the end would cause unnecessary contention when large amount of memory blocks are inserted simultaneous by multiple threads. -The data structure refering to this single linked list cover two cache +The data structure referring to this single linked list cover two cache lines. One cache line containing information about the head of the list, and one cache line containing information about the tail of the list. This in order to reduce cache line ping ponging of this data @@ -65,21 +65,21 @@ list. In the uncontended case it will point to the end of the list, but when simultaneous insert operations are performed it will point to something near the end of the list. -When insterting an element one will try to write a pointer to the new +When inserting an element one will try to write a pointer to the new element in the next pointer of the element pointed to by the last pointer. This is done using an atomic compare and swap that expects -the next pointer to be `NULL`. If this succeds the thread performing +the next pointer to be `NULL`. If this succeeds the thread performing this operation moves the last pointer to point to the newly inserted element. If the atomic compare and swap described above failed, the last pointer didn't point to the last element. In this case we need to -insert the new element somewhere inbetween the element that the last +insert the new element somewhere between the element that the last pointer pointed to and the actual last element. If we do it this way the last pointer will eventually end up at the last element when threads stop adding new elements. When trying to insert somewhere near the end and failing to do so, the inserting thread sometimes moves to -the next element and somtimes tries with the same element again. This +the next element and sometimes tries with the same element again. This in order to spread the inserted elements during heavy contention. That is, we try to spread the modifications of memory to different locations instead of letting all threads continue to try to modify the @@ -87,7 +87,7 @@ same location in memory. ### Head ### -The head contains pointers to begining of the list (`head.first`), and +The head contains pointers to beginning of the list (`head.first`), and to the first block which other threads may refer to (`head.unref_end`). Blocks between these pointers are only refered to by the head part of the data structure which is only used by the @@ -142,7 +142,7 @@ contains this "marker" element. ### Contention ### -When elements are continously inserted by threads not owning the +When elements are continuously inserted by threads not owning the allocator instance, the thread owning the allocator instance will be able to work more or less undisturbed by other threads at the head end of the list. At the tail end large amounts of simultaneous inserts may |