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Merge "Change all references to PSS to RSS."

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Christopher Ferris 2019-08-08 04:14:15 +00:00 committed by Gerrit Code Review
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docs/native_allocator.md
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@ -10,7 +10,7 @@ at least the
It is important to note that there are two modes for a native allocator
to run in on Android. The first is the normal allocator, the second is
called the svelte config, which is designed to run on memory constrained
systems and be a bit slower, but take less PSS. To enable the svelte config,
systems and be a bit slower, but take less RSS. To enable the svelte config,
add this line to the `BoardConfig.mk` for the given target:
MALLOC_SVELTE := true
@ -55,7 +55,7 @@ to work efficiently.
When set to zero, `mallopt(M_DECAY_TIME, 0)`, it is expected that an
allocator will attempt to purge and release any unused memory back to the
kernel on free calls. This is important in Android to avoid consuming extra
PSS.
RSS.
When set to non-zero, `mallopt(M_DECAY_TIME, 1)`, an allocator can delay the
purge and release action. The amount of delay is up to the allocator
@ -65,13 +65,13 @@ allocator was implemented to have a one second delay.
The drawback to this option is that most allocators do not have a separate
thread to handle the purge, so the decay is only handled when an
allocation operation occurs. For server processes, this can mean that
PSS is slightly higher when the server is waiting for the next connection
RSS is slightly higher when the server is waiting for the next connection
and no other allocation calls are made. The `M_PURGE` option is used to
force a purge in this case.
For all applications on Android, the call `mallopt(M_DECAY_TIME, 1)` is
made by default. The idea is that it allows application frees to run a
bit faster, while only increasing PSS a bit.
bit faster, while only increasing RSS a bit.
#### M\_PURGE
When called, `mallopt(M_PURGE, 0)`, an allocator should purge and release
@ -115,7 +115,7 @@ to specify a device.
## Performance
There are multiple different ways to evaluate the performance of a native
allocator on Android. One is allocation speed in various different scenarios,
anoher is total PSS taken by the allocator.
another is total RSS taken by the allocator.
The last is virtual address space consumed in 32 bit applications. There is
a limited amount of address space available in 32 bit apps, and there have
@ -129,7 +129,7 @@ benchmarks. These benchmarks can be built using this command:
mmma -j bionic/benchmarks
These benchmarks are only used to verify the speed of the allocator and
ignore anything related to PSS and virtual address space consumed.
ignore anything related to RSS and virtual address space consumed.
#### Allocate/Free Benchmarks
These are the benchmarks to verify the allocation speed of a loop doing a
@ -228,7 +228,7 @@ To run the benchmarks with `mallopt(M_DECAY_TIME, 1)`, use these commands:
These numbers should be as performant as the current allocator.
### Memory Trace Benchmarks
These benchmarks measure all three axes of a native allocator, PSS, virtual
These benchmarks measure all three axes of a native allocator, RSS, virtual
address space consumed, speed of allocation. They are designed to
run on a trace of the allocations from a real world application or system
process.
@ -248,7 +248,7 @@ And these two benchmark executables:
/data/benchmarktest/trace_benchmark/trace_benchmark
#### Memory Replay Benchmarks
These benchmarks display PSS, virtual memory consumed (VA space), and do a
These benchmarks display RSS, virtual memory consumed (VA space), and do a
bit of performance testing on actual traces taken from running applications.
The trace data includes what thread does each operation, so the replay
@ -279,8 +279,8 @@ Run the benchmark thusly:
Where XXX.txt is the name of a trace file.
Every 100000 allocation operations, a dump of the PSS and VA space will be
performed. At the end, a final PSS and VA space number will be printed.
Every 100000 allocation operations, a dump of the RSS and VA space will be
performed. At the end, a final RSS and VA space number will be printed.
For the most part, the intermediate data can be ignored, but it is always
a good idea to look over the data to verify that no strange spikes are
occurring.
@ -304,6 +304,14 @@ important to verify that when running this trace using the 32 bit replay
executable, the virtual address space consumed is not much larger than the
current allocator. A small increase (on the order of a few MBs) would be okay.
There is no specific benchmark for memory fragmentation, instead, the RSS
when running the memory traces acts as a proxy for this. An allocator that
is fragmenting badly will show an increase in RSS. The best trace for
tracking fragmentation is system\_server.txt which is an extremely long
trace (~13 million operations). The total number of live allocations goes
up and down a bit, but stays mostly the same so an allocator that fragments
badly would likely show an abnormal increase in RSS on this trace.
NOTE: When a native allocator calls mmap, it is expected that the allocator
will name the map using the call: