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Fix computing available memory on OSX for GC - #97102
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We were using the `vm_statistics_data_t::free_count` as the available memory reported to the GC. It turned out this value is only a small portion of the available memory and that the appropriate value should be based on the kern.memorystatus_level value obtained using sysctl. That value represents percentual amount of available memory, so multiplying it by the total memory bytes gets the available memory bytes. Closedotnet#94846
ghost
commented
Jan 17, 2024
Tagging subscribers to this area: @dotnet/gc Issue DetailsWe were using the Close #94846
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| int rc = sysctlnametomib(mem_free_name, NULL, &g_kern_memorystatus_level_mib_length); | ||
| if (rc == 0) | ||
| { | ||
| g_kern_memorystatus_level_mib = (int*)malloc(g_kern_memorystatus_level_mib_length * sizeof(int)); |
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presumably if this returns null then sysctlnametomib would return a failure?
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Thank you for spotting the missing check, fixed.
| if (KERN_SUCCESS == host_page_size(mach_port, &page_size)) | ||
| uint32_t mem_free = 0; | ||
| size_t mem_free_length = sizeof(uint32_t); | ||
| if (g_kern_memorystatus_level_mib != NULL) |
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if GCToOSInterface::Initialize succeeded, this should always be non null, correct? if so we can just assert.
| int64_t mem_size = 0; | ||
| size_t mem_size_length = sizeof(int64_t); | ||
| int mib[] = { CTL_HW, HW_MEMSIZE }; | ||
| rc = sysctl(mib, 2, &mem_size, &mem_size_length, NULL, 0); |
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do we need to get the total memory every time?
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Good point, I've moved it to the init and also unified it with other total memory computations we had above.
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We were using the
vm_statistics_data_t::free_countas the available memory reported to the GC. It turned out this value is only a small portion of the available memory and that the appropriate value should be based on the kern.memorystatus_level value obtained using sysctl. That value represents percentual amount of available memory, so multiplying it by the total memory bytes gets the available memory bytes.Close#94846