![]() ![]() ![]() Swap space doesn’t perform identically to real memory, though, because the read and write speeds of physical RAM are much higher than most storage devices. The total amount of virtual memory that’s usable is thus comprised of the real memory plus the swap space. Image credits: Ehamberg/Wikipedia.Īn added benefit of this abstraction is that a portion of the storage device can be reserved for use as virtual memory (called the swap space). Virtual memory combines physical RAM and swap space on storage devices. This way, apps don’t have to worry about where their data is actually being stored in real memory. Apps instead reference virtual memory locations using a virtual memory address, and the system handles the mapping between virtual addresses and the actual location they point to in real memory. With virtual memory, the system handles memory management. That’s just one of the many problems with letting apps specify the memory addresses they’ll use, and it’s partly why most modern systems implement virtual memory. This is because apps would overallocate memory for fear of not having enough. If apps were given free reign to reserve an explicit range of memory addresses for their execution, then we’d quickly run into memory allocation problems. When you launch an app on your phone, its code is loaded into memory as a process, as are any files they’re accessing. The location of each byte of data (4GB means 4294967296 or 2 32 bytes) is referenced by an address, the total number of which is called the address space (for a 4GB RAM system, the addresses would range from 0 to 2 32 -1). The total amount of real memory is finite, so a phone advertised as having 4GB of RAM has 4 gigabytes of real memory to work with. Real memory refers to the actual, physical memory (RAM) that’s in the device. You only need to know a few concepts to understand how multi-gen LRU improves things, fortunately.įirst of all, we need to talk about the difference between real memory and virtual memory. Linux’s memory management subsystem is extremely complex, so explaining every term and parameter would take forever. Esper for Developers How Linux views memoryīefore I talk about multi-generational LRU, I first need to explain the basics of how Linux manages memory, and I mean the basics. In this week’s edition of Android Dessert Bites, I’ll explain how Linux’s memory management is getting better with multi-gen LRU, and how this trickles down to better performance for Android devices. ![]() Linux’s new multi-generational LRU framework, developed by Google, stands to vastly improve the kernel’s page reclaim strategy, yielding substantial improvements to memory management and CPU use. Like every new Android release, Android 13 has a couple of performance-related optimizations here and there, but one of the most impactful improvements may be coming from an update to the underlying Linux kernel. Performance improvements are particularly hard to notice, even if they can be quantified. The ratio of user-facing features to developer APIs in each new version varies tremendously, but most changes are actually invisible to users. Each Android version update comes with a boatload of changes, some more than others. ![]()
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