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5918976
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2011-05-07T03:46:10.483
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2011-05-07T15:14:08.727
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2011-05-07T15:14:08.727
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5839626
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2
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It takes some digging through the source to figure it out, but Top uses the task_info() call to interface with the Mach kernel and gather memory statistics. You can read some mostly correct information about task_info() at <a href="http://www.gnu.org/software/hurd/gnumach-doc/Task-Information.html" rel="nofollow">http://www.gnu.org/software/hurd/gnumach-doc/Task-Information.html</a>. I say mostly correct because there's at least one difference I've found in the OS X implementation: memory sizes are reported in bytes, not pages. As a summary, you pass task_info() a "target task" (mach_task_self() if you want information about your program itself, otherwise use task_for_pid() or processor_set_tasks()) and tell it you want "basic info," the category under which virtual and resident memory sizes fall. Then task_info() fills in a task_basic_info struct with the information you want. Here's a class I wrote to get the resident memory size. It also shows how you can use sysctl to get information about your system (how much physical ram you have, in this instance): <pre><code>#include <sys/sysctl.h> #include <mach/mach.h> #include <cstdio> #include <stdint.h> #include <unistd.h> //////////////////////////////////////////////////////////////////////////////// /*! Class for retrieving memory usage and system memory statistics on Mac OS X. // (Or probably any system using the MACH kernel.) */////////////////////////////////////////////////////////////////////////////// class MemoryInfo { public: /** Total amount of physical memory (bytes) */ uint64_t physicalMem; //////////////////////////////////////////////////////////////////////// /*! Constructor queries various memory properties of the system */////////////////////////////////////////////////////////////////////// MemoryInfo() { int mib[2]; mib[0] = CTL_HW; mib[1] = HW_MEMSIZE; size_t returnSize = sizeof(physicalMem); if (sysctl(mib, 2, &physicalMem, &returnSize, NULL, 0) == -1) perror("Error in sysctl call"); } //////////////////////////////////////////////////////////////////////// /*! Queries the kernel for the amount of resident memory in bytes. // @return amount of resident memory (bytes) */////////////////////////////////////////////////////////////////////// static size_t Usage(void) { task_t targetTask = mach_task_self(); struct task_basic_info ti; mach_msg_type_number_t count = TASK_BASIC_INFO_64_COUNT; kern_return_t kr = task_info(targetTask, TASK_BASIC_INFO_64, (task_info_t) &ti, &count); if (kr != KERN_SUCCESS) { printf("Kernel returned error during memory usage query"); return -1; } // On Mac OS X, the resident_size is in bytes, not pages! // (This differs from the GNU Mach kernel) return ti.resident_size; } }; </code></pre>
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1. POHow is top able to see memory usage
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1. USJulian Panetta
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1. USJulian Panetta
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