Unity provides several allocator types, where each type represents a different relative prioritization of the following key factors:
If an application has a lot of spare memory, it can use faster, memory-heavy allocators when it loads scenesA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary and frames. However, the more an application’s memory is limited, the more efficiently it must use the memory available, which often means using slower allocators.
To help you get the best performance for different projects, you can customize Unity’s allocators to fit the size and requirements of each application.
Unity uses different allocator types, which all use different algorithms to organize memory. Unity’s memory manager uses these allocator types in different areas to organize the memory in your application effectively. You can adjust the size of each allocation for each area, either through the Player settingsSettings that let you set various player-specific options for the final game built by Unity. More info
See in Glossary window in the Unity Editor, or through the command line.
The different types of allocators are as follows:
Each allocator type has a different algorithm for fitting allocations into blocks of memory, and is therefore useful for different types of allocations. The important difference between allocations is usually persistence, or allocation lifespan, which determines where to put an allocation. For example, a long-lived (persistent) allocation goes to the heap and bucket allocators, while short-lived allocations go to the thread-safe linear and thread local storage allocators.
When an allocation is made somewhere in code, Unity does the following:
The dual thread allocator is used for longer lived allocations and those that need to be passed between threads, such as graphics allocations that need passing from the main thread to the render thread.
The allocator contains two dynamic heap allocators: a lock-free one for the main thread, and one for all other threads, which locks on allocation and deallocation. It also contains a bucket allocator for small, long-lived allocations.
Unity creates several dual thread allocators by default, including the Main and Gfx dual thread allocators. File cache and ProfilerA window that helps you to optimize your game. It shows how much time is spent in the various areas of your game. For example, it can report the percentage of time spent rendering, animating, or in your game logic. More info
See in Glossary allocations are always dynamic heap allocations.
For an example of dual thread allocator usage refer to Dual thread allocator example.
The dynamic heap allocator is the main heap allocator. It uses a Two Level Segregated Fit (TLSF) algorithm to manage its memory. It’s used for large, long-lived allocations and for allocations that can’t fit in the bucket allocator. The allocations are divided into memory blocks of a given size, which are requested as needed. An allocation must be smaller than half a block. An allocation of half a block or more is too large for the dynamic heap allocator and in such cases Unity uses the virtual memory API to make the allocation instead.
For an example of the dynamic heap allocator usage, refer to Dynamic heap allocator example.
The bucket allocator is a fast lock-free allocator that performs small allocations. The dual thread allocator uses the bucket allocator for small, long-lived allocations. These allocations prevent small ones from fragmenting the dynamic heap allocators.
The bucket allocator reserves blocks of memory for allocations. Each block is divided into subsections of 16 KB. This isn’t configurable, and doesn’t appear in the user interface. Each subsection is divided into allocations. The allocation size is a multiple of a configured fixed size, called granularity. The bucket allocator has a maximum number of blocks of a given size.
Important: The bucket allocator behaves differently between development and release builds, due to an additional 40 byte header in the development buildA development build includes debug symbols and enables the Profiler. More info
See in Glossary.
For an example of the bucket allocator usage, refer to Bucket allocator example.
The Thread local storage (TLS) stack allocator is for per thread short-lived allocations. It’s the fastest allocator. It consists of last-in-first-out (LIFO) memory stacks that set each stack pointer to 0 to clear memory. The TLS allocator is mostly used for Allocator.Temp
allocations, which can also come from user-written code.
The default block size for the thread local storage (TLS) stack allocator is 4 MB for platforms and 16 MB for the Unity Editor. You can customize these values. If the allocator usage exceeds the configured block size, Unity increases the block size. The limit for this increase is twice the original size.
The TLS stack allocator’s memory allocations ideally live for less than a frame and have a similar lifespan as their encompassing scope.
Because TLS is a stack allocator, interleaved allocation and deallocation patterns (for example, allocate a, allocate b, deallocate a, alloctate c, deallocate b, etc.) can fragment it and stop the allocator from resetting the stack point down-stack. This might cause it to fill up entirely while theoretically having free space available.
If a thread’s stack allocator is full, allocations fall back to the threadsafe linear allocator.
For an example of the TLS stack allocator usage, refer to Thread local storage stack allocator example.
The thread-safe linear allocator is a fallback for the TLS stack allocator, and it allocates up to 16 blocks of memory. It uses a first-in-first-out (FIFO) algorithm for lock-free allocations of work buffers for jobs. When complete, the jobs dispose of these buffers. It’s mostly used for Allocator.TempJob
allocations, which have a 4 frame lifetime limit, and they can also come from user-written code.
This allocator allocates blocks of memory, then linearly allocates memory within those blocks. Available blocks are held in a pool. When one block is full, the allocator fetches a new block from the pool. When the allocator no longer needs the memory in a block, it clears the block, and the block returns to the pool of available blocks. It’s important to clear allocations quickly to make blocks available again, so a job should not stay allocated for more than a few frames.
If all blocks of memory are full, the allocations fall back to the main dual thread allocator, which is a much slower allocator.
For an example of thread-safe linear allocator usage refer to Thread safe linear allocator example.
Did you find this page useful? Please give it a rating:
Thanks for rating this page!
What kind of problem would you like to report?
Thanks for letting us know! This page has been marked for review based on your feedback.
If you have time, you can provide more information to help us fix the problem faster.
Provide more information
You've told us this page needs code samples. If you'd like to help us further, you could provide a code sample, or tell us about what kind of code sample you'd like to see:
You've told us there are code samples on this page which don't work. If you know how to fix it, or have something better we could use instead, please let us know:
You've told us there is information missing from this page. Please tell us more about what's missing:
You've told us there is incorrect information on this page. If you know what we should change to make it correct, please tell us:
You've told us this page has unclear or confusing information. Please tell us more about what you found unclear or confusing, or let us know how we could make it clearer:
You've told us there is a spelling or grammar error on this page. Please tell us what's wrong:
You've told us this page has a problem. Please tell us more about what's wrong:
Thank you for helping to make the Unity documentation better!
Your feedback has been submitted as a ticket for our documentation team to review.
We are not able to reply to every ticket submitted.
When you visit any website, it may store or retrieve information on your browser, mostly in the form of cookies. This information might be about you, your preferences or your device and is mostly used to make the site work as you expect it to. The information does not usually directly identify you, but it can give you a more personalized web experience. Because we respect your right to privacy, you can choose not to allow some types of cookies. Click on the different category headings to find out more and change our default settings. However, blocking some types of cookies may impact your experience of the site and the services we are able to offer.
More information
These cookies enable the website to provide enhanced functionality and personalisation. They may be set by us or by third party providers whose services we have added to our pages. If you do not allow these cookies then some or all of these services may not function properly.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
These cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. If you do not allow these cookies, you will experience less targeted advertising. Some 3rd party video providers do not allow video views without targeting cookies. If you are experiencing difficulty viewing a video, you will need to set your cookie preferences for targeting to yes if you wish to view videos from these providers. Unity does not control this.
These cookies are necessary for the website to function and cannot be switched off in our systems. They are usually only set in response to actions made by you which amount to a request for services, such as setting your privacy preferences, logging in or filling in forms. You can set your browser to block or alert you about these cookies, but some parts of the site will not then work. These cookies do not store any personally identifiable information.