This would create a more flexible solution, but presents a similar problem to the compile-time one. Note that 5 memory regions are leaked - more mallocs than frees. At this point all the callers in Gecko use a power-of-two size, so there's no benefit to be had for Firefox. If --enable-stats is specified during configuration, this has the potential to cause deadlock for a multi-threaded process that exits while one or more threads are executing in the memory allocation functions. Although the excess bytes can be overwritten by the application without ill effects, this is not good programming practice: the number of excess bytes in an allocation depends on the underlying implementation. This alignment makes it possible to find metadata for user objects very quickly.
Are you sure that you want those removed? This matches a performance pattern I have observed: the standard C libraries under Linux have very fast memory allocation compared to Apple platforms. But that would be the answer to a different question! Obviously you can decide to subtract 1 in the macro so the number agrees exactly with mallinfo. What do you think of this simplification? For example, if you call malloc 1 , you should not assume that only one byte was allocated. The real memory usage has dropped by 11%. Behavior is undefined if size is not an integral multiple of alignment. Note that using substantially more arenas than the default is not likely to improve performance, mainly due to reduced cache performance. What do you think of this simplification? Please note that doing anything which tries to allocate memory in this function is likely to result in a crash or deadlock.
Small objects are managed in groups by page runs. Note that realloc may move the memory allocation, resulting in a different return value than ptr. In addition to multiple arenas, unless --disable-tcache is specified during configuration, this allocator supports thread-specific caching for small and large objects, in order to make it possible to completely avoid synchronization for most allocation requests. To avoid corruption in multithreaded applications, mutexes are used internally to protect the memory-management data structures employed by these functions. Please provide any additional information below. If this option is enabled, every unique backtrace must be stored for the duration of execution. This option is enabled by default.
At a minimum, all small size classes are cached, and at a maximum all large size classes are cached. If enabled, use an function to report memory leaks detected by allocation sampling. My answer even got downvoted. Memory is conceptually broken into equal-sized chunks, where the chunk size is a power of two that is greater than the page size. The main use of this function is for debugging and introspection.
The reallocarray function changes the size of the memory block pointed to by ptr to be large enough for an array of nmemb elements, each of which is size bytes. The realloc function always leaves the original buffer intact when an error occurs. A description of the project, information about reporting bugs, and the latest version of this page, can be found at. This is intended for debugging and will impact performance negatively. Otherwise, or if free ptr has already been called before, undefined behavior occurs. I collected these by starting the browser, running Tdhtml, and immediately stopping the browser.
I added that line out of curiosity after seeing fanl's answer. Errors will result in the process dumping core. All other small object size classes are multiples of the quantum, spaced such that internal fragmentation is limited to approximately 25% for all but the smallest size classes. Let me know if you need anything else : Reported by decoder. Chunks are always aligned to multiples of the chunk size. What do you think of this simplification? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. I'm not really sure how any version of this code ever worked.
The free function frees the memory space pointed to by ptr, which must have been returned by a previous call to malloc , calloc , or realloc. To scalably handle memory allocation in multithreaded applications, glibc creates additional memory allocation arenas if mutex contention is detected. This is intended for debugging and will impact performance negatively. Note that even during huge allocation this setting is read from the arena that would be chosen for small or large allocation so that applications can depend on consistent dss versus mmap allocation regardless of allocation size. The malloc implementation is tunable via environment variables; see for details. Would you mind helping us to port this to 3.
So unless you want to dive in the malloc functionality, I recommend you just save the size of the allocation yourself. Posted patch — — I would like to emphasize the importance of this small patch by reiterating the performance and memory footprint benefits it gives on Firefox. Profiles are dumped to files named according to the pattern. The mallctl, mallctlnametomib, and mallctlbymib functions return 0 on success; otherwise they return an error value. Most malloc'd memory regions do.