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| | == Outline == | | == Outline == |
| − | * Title
| + | See [[Improving Android Boot Time Outline]] |
| − | * Outline
| + | |
| − | ** Android boot overview
| + | |
| − | ** Measuring boot times
| + | |
| − | ** Problem areas
| + | |
| − | *** Some gory details
| + | |
| − | ** Ideas for improvements
| + | |
| − | * Android boot overview
| + | |
| − | ** bootloader
| + | |
| − | ** kernel
| + | |
| − | ** init
| + | |
| − | ** zygote
| + | |
| − | *** building preload heap
| + | |
| − | *** start package manager
| + | |
| − | ** service manager
| + | |
| − | *** start services
| + | |
| − | * measuring bootup time
| + | |
| − | ** systems measured: adp1, n1, evm
| + | |
| − | *** adp1 with donut
| + | |
| − | *** n1 with eclair
| + | |
| − | *** evm with eclair
| + | |
| − | **** NOTE: used nfs root filesystem (file IO timings might be bogus)
| + | |
| − | * Tools for measuring and tracing boot time
| + | |
| − | ** stopwatch
| + | |
| − | ** grabserial
| + | |
| − | ** printk times
| + | |
| − | ** bootchart
| + | |
| − | ** strace
| + | |
| − | ** logcat
| + | |
| − | ** method tracer*
| + | |
| − | ** ftrace*
| + | |
| − | * stopwatch
| + | |
| − | * grabserial
| + | |
| − | * printk times
| + | |
| − | * bootchart
| + | |
| − | * strace
| + | |
| − | * logcat
| + | |
| − | ** extra instrumentation for preloading classes
| + | |
| − | ** PARSE_CHATTY flag for package scanning
| + | |
| − | ** mention my own tool 'logdelta'
| + | |
| − | * method tracer*
| + | |
| − | ** method traces is built in to
| + | |
| − | ** ftrace?? (no)
| + | |
| − | * Problem Areas
| + | |
| − | ** First, a bootchart for EVM board
| + | |
| − | ** bootloader init
| + | |
| − | ** kernel init
| + | |
| − | ** zygote class preloading
| + | |
| − | ** package scanning
| + | |
| − | ** service initialization
| + | |
| − | * bootloader init
| + | |
| − | ** outside scope of this talk
| + | |
| − | ** didn't measure commercial bootloader, only development one (U-boot)
| + | |
| − | * kernel init
| + | |
| − | ** is mostly the usual suspects
| + | |
| − | ** (initcall_debug results)
| + | |
| − | ** USB
| + | |
| − | * zygote class preloading
| + | |
| − | ** zygote pre-loads just under 2000 classes, and instantiates them in its heap
| + | |
| − | ** controlled by file:
| + | |
| − | * package manager package scan
| + | |
| − | ** exact purpose is not known
| + | |
| − | *** validation of certificates, permissions, capabilities and dependencies, etc.?
| + | |
| − | ** EVERY package is scanned at boot time
| + | |
| − | * ideas for enhancements
| + | |
| − | ** kernel speedups
| + | |
| − | ** optimize package scan
| + | |
| − | ** optimize class preloading
| + | |
| − | ** miscellaneous optimizations
| + | |
| − | ** sreadahead??
| + | |
| − | * kernel speedups
| + | |
| − | ** outside the scope of this presentation
| + | |
| − | ** see http://elinux.org/Boot_Time
| + | |
| − | * optimize package scan
| + | |
| − | *** most definitely
| + | |
| − | *** need to continue analysis
| + | |
| − | **** most likely, should switch to a compressed flash file system
| + | |
| − | ** use pre-constructed dalvik heap? (difficult?)
| + | |
| − | *** thread the heap construction?
| + | |
| − | * sreadahead??
| + | |
| − | ** could use sreadahead to pre-fill page cache
| + | |
| − | ** however, this just masks bad behavior
| + | |
| − | *** Contacts.apk (half of 1.6M) is read 4 times! during boot
| + | |
| − | *** filling page cache makes reads after first one fast, but it would be better to avoid all these reads altogether
| + | |
| − | **** better to just optimize or eliminate parseZipArchive()
| + | |
| − | ** sreadahead should be used dead last (after all other enhancements)
| + | |
| − | | + | |
| − | - don't know how to preconstruct heap
| + | |
| − | - need to analyze heap
| + | |
| − | - FIXTHIS - is heap identical on every boot?
| + | |
| − | - how to dump heap memory
| + | |
| − | - how to dump any memory in Android??
| + | |
| − | - are parts identical??
| + | |
| − | - zoneinfo inefficiencies
| + | |
| − | - measure without strace, and see if time is a problem
| + | |
| − | - remaining questions
| + | |
| − | - future directions
| + | |
This page has notes and materials in support of Tim Bird's presentation "Improving Android Bootup Time",
which he is gave at LinuxCon North America, 2010.
Android is a relatively new distribution of Linux, with a completely different user space implementation, compared to desktop or enterprise Linux. It also has some rather horrible boot times. But it's popular - so Tim decided to take a look and see if the bootup time of a standard Android system could be improved. This presentation describes how well he succeeded in this venture. Tim will present methods of measuring kernel and user-space bootup time on an Android system, as well as present some ideas for places where Android bootup time could be improved.
