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Use sysconf(_SC_NPROCESSORS_CONF) in PAL and GC ONLY on ARM and ARM64 #18289

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Jun 5, 2018
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Use sysconf(_SC_NPROCESSORS_CONF) in PAL and GC ONLY on ARM and ARM64 #18289

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8 changes: 7 additions & 1 deletion src/gc/unix/gcenv.unix.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,12 @@
#include <unistd.h> // sysconf
#include "globals.h"

#if defined(_ARM_) || defined(_ARM64_)
#define SYSCONF_GET_NUMPROCS _SC_NPROCESSORS_CONF
#else
#define SYSCONF_GET_NUMPROCS _SC_NPROCESSORS_ONLN
#endif

// The cachced number of logical CPUs observed.
static uint32_t g_logicalCpuCount = 0;

Expand Down Expand Up @@ -67,7 +73,7 @@ bool GCToOSInterface::Initialize()
g_pageSizeUnixInl = uint32_t((pageSize > 0) ? pageSize : 0x1000);

// Calculate and cache the number of processors on this machine
int cpuCount = sysconf(_SC_NPROCESSORS_CONF);
int cpuCount = sysconf(SYSCONF_GET_NUMPROCS);
if (cpuCount == -1)
{
return false;
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12 changes: 10 additions & 2 deletions src/pal/src/misc/sysinfo.cpp
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Expand Up @@ -103,10 +103,18 @@ PAL_GetLogicalCpuCountFromOS()
int nrcpus = 0;

#if HAVE_SYSCONF
nrcpus = sysconf(_SC_NPROCESSORS_CONF);

#if defined(_ARM_) || defined(_ARM64_)
#define SYSCONF_GET_NUMPROCS _SC_NPROCESSORS_CONF
#define SYSCONF_GET_NUMPROCS_NAME "_SC_NPROCESSORS_CONF"
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A nit - instead of defining the macro and its string version, you can define a stringification macro that will make the conversion automatically:

#define STRINGIFY1(s) #s
#define STRINGIFY(s) STRINGIFY1(s)

Then you can write the assert like this:

ASSERT("sysconf failed for %s (%d)\n", STRINGIFY(SYSCONF_GET_NUMPROCS), errno);

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Actually, I though about this once but I could not justify doing stringification instead of hard-coding names of the variables.

Unfortunately, doing stringification your way would not work for this example

#define _SC_NPROCESSORS_CONF 57
#define _SC_NPROCESSORS_ONLN 58

#define SYSCONF_GET_NUMPROCS       _SC_NPROCESSORS_CONF 
//#define SYSCONF_GET_NUMPROCS       _SC_NPROCESSORS_ONLN

#define STRINGIFY1(s) #s
#define STRINGIFY(s) STRINGIFY1(s)

int main()
{
    printf("STRINGIFY(SYSCONF_GET_NUMPROCS) is %s\n", STRINGIFY(SYSCONF_GET_NUMPROCS)); // Output: STRINGIFY(SYSCONF_GET_NUMPROCS) is 57
    return 0;
}

This is how SC_NPROCESSORS_CONF is defined in FreeBSD https://github.com/freebsd/freebsd/blob/06362ad468fc11671364e34ed413ea9c19d858f1/include/unistd.h#L292

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Ok, thanks, forget about it then.

#else
#define SYSCONF_GET_NUMPROCS _SC_NPROCESSORS_ONLN
#define SYSCONF_GET_NUMPROCS_NAME "_SC_NPROCESSORS_ONLN"
#endif
nrcpus = sysconf(SYSCONF_GET_NUMPROCS);
if (nrcpus < 1)
{
ASSERT("sysconf failed for _SC_NPROCESSORS_CONF (%d)\n", errno);
ASSERT("sysconf failed for %s (%d)\n", SYSCONF_GET_NUMPROCS_NAME, errno);
}
#elif HAVE_SYSCTL
int rc;
Expand Down