jwmalloc: A Verified Memory Allocator for Mobile Devices

Dynamic memory allocators provide memory allocation and release functionality to languages such as C, C++, and Rust. Existing allocators have been primarily optimized for performance and timely memory release. However, emerging mobile workloads also emphasize CPU, energy, and memory usage under soft real-time constraints.

We present jwmalloc, a novel memory allocator built from the ground up to address these mobile-specific challenges. It is based on three key innovations: a uniform slab size with pooling that enables immediate cross-size-class reuse of any emptied slab; the closed sibling tree, a new data structure for efficiently managing fragments; and a two-buffer lifetime tracker that categorizes short-and long-lived objects to guide memory reclamation. For timely response in soft real-time and oversubscription scenarios, all operations are non-blocking. We verified jwmalloc with a bounded model checker under weak memory models. Replacing jemalloc on a flagship smartphone running real-world workloads, jwmalloc reduces wholesystem instructions by 10% and cuts allocator-side instruction counts by 3.84×, while lowering CPU power consumption by 5-11%, all at a comparable memory footprint. jwmalloc has been deployed in production on 12 million commercial mobile devices, operating stably for over 30 billion user hours.

Open the app market, search for and install a specific app, then uninstall the app. browser1

Open a browser app, enter a URL, and stay on the page. browser2

Open a browser app, enter a URL, and scroll the web page. camera_record Open the camera app, switch to video mode, and start recording. game_center Open the game center app, browse its home screen, then exit the app. ebook_reading Open a reader app, open the first book, and turn pages. input_method Swipe down from the home screen, tap the search box, and search for a keyword. location Open the device-finding app and refresh the location. map Open a map app, search for a keyword, and start navigation. mms1

Open the messages app, enter the message list, view the first message, and scroll back. mms2

Open the messages app, enter the message list, and scroll. music1

Open a music app and play a local audio file. music2

Open a music app and play local music with the screen off. music3

Open a music app, enter the local song list, and scroll the list. notepad Open the notepad app, create a new note, and switch between tabs. photo_library Open the photo library, tap "Albums", tap "Photos", enter the thumbnail view, and scroll. home_screen1

Enter an enlarged folder, swipe once, and exit. home_screen2

Launch the settings app and swipe up to send it to the background. home_screen3

Continuously launch Settings, Notepad, Messages, Phone, and Calendar; enter the multitasking interface and repeatedly swipe. home_screen4

Repeatedly increase and decrease the volume. home_screen5

Repeatedly pull down the control center and then exit it. home_screen6

Enter the minus-one screen (leftmost panel) and repeatedly swipe. home_screen7

Enter an enlarged folder, then repeatedly open and exit it. screen_record From the home screen, pull down the control center, tap screen recording, record a clip, then stop and return to the home screen. setting1

Open the settings app and repeatedly swipe. setting2

Open the settings app, log in to the account, tap "Scan", select a QR code from Photos, and scan. floating_window Open the settings app, swipe up to the floating-window area, and release to create a floating window. theme_manager Open the theme app and repeatedly swipe on the home page. shopping1

Open a shopping app and scroll down to browse products. shopping2

Open a shopping app, enter the "Me" page, and swipe. weather1

Open the weather app and send it to the background. weather2

Open the weather app and swipe left to switch cities.