Programmatically get the cache line size on Android

Question

How do I get the cache line size on ARM Android? This is equivalent to the following page but specifically for Android:

Programmatically get the cache line size?

The answers on that page, and other ways I knew, do not work on Android:

/sys/devices/system/cpu/cpu0/cache/ does not exist.
_SC_LEVEL1_DCACHE_LINESIZE does not exist as a sysconf parameter, even if I manually pass in the value 190.
AT_DCACHEBSIZE does not exist as a getauxval parameter, even if I manually pass in the value 19.
/proc/cpuinfo does not contain cache line information.

Unlike x86, ARM's CPU information is only available in kernel mode, so there's no cpuid equivalent available to applications.

Did you get the answer? I'm facing the same problem. – Netherwire Feb 22 '20 at 17:53 — Netherwire, Feb 22 '20 at 17:53

Netherwire · Accepted Answer · 2020-02-22T22:16:14.633

I carried out a small investigation and found something:

First of all, it seems like sysconf() with _SC_LEVEL1_ICACHE_SIZE, _SC_LEVEL1_ICACHE_ASSOC, _SC_LEVEL1_ICACHE_LINESIZE or other CPU cache-related flags always returns -1 (sometimes it could be 0) and it seems to be the reason for this, they're simply not implemented.

But there's a solution. Use this library if you're able to use JNI in your project. This library is extremely helpful to retrieve information about the CPU (my device's as old as hills):

Here's the code I used to obtain information about my CPU caches:

#include <string>
#include <sstream>
#include <cpuinfo.h>

void get_cache_info(const char* name, const struct cpuinfo_cache* cache, std::ostringstream& oss)
{
    oss << "CPU Cache: " << name << std::endl;
    oss << " > size            : " << cache->size << std::endl;
    oss << " > associativity   : " << cache->associativity << std::endl;
    oss << " > sets            : " << cache->sets << std::endl;
    oss << " > partitions      : " << cache->partitions << std::endl;
    oss << " > line_size       : " << cache->line_size << std::endl;
    oss << " > flags           : " << cache->flags << std::endl;
    oss << " > processor_start : " << cache->processor_start << std::endl;
    oss << " > processor_count : " << cache->processor_count << std::endl;
    oss << std::endl;
}

const std::string get_cpu_info()
{
    cpuinfo_initialize();
    const struct cpuinfo_processor* proc = cpuinfo_get_current_processor();

    std::ostringstream oss;

    if (proc->cache.l1d)
        get_cache_info("L1 Data", proc->cache.l1d, oss);

    if (proc->cache.l1i)
        get_cache_info("L1 Instruction", proc->cache.l1i, oss);

    if (proc->cache.l2)
        get_cache_info("L2", proc->cache.l2, oss);

    if (proc->cache.l3)
        get_cache_info("L3", proc->cache.l3, oss);

    if (proc->cache.l4)
        get_cache_info("L4", proc->cache.l4, oss);

    return oss.str();
}

Programmatically get the cache line size on Android

1 Answers1