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Tag: memory

understand sysstat sar memory output

I’m preparing for more traffic in the days to come, and I want to be sure server can handle it. Running sar -q, the load of “3.5” doesn’t seem much on 32 CPU architecture: However, I’m not sure about the memory. Running sar -r shows 98.5% for the %memused and only 13.60 for %commit: running htop seems OK too: 14.9G/126G.

Is there a different memory allocation path other than the buddy allocator in linux?

I’m understanding memory allocation in Linux and doing some changes in buddy allocator (__alloc_pages_nodemask) for my experiments. I create a new flag in struct page->flags (by adding a new flag in enum pageflags in page-flags.h. I set this bit permanently in __alloc_pages_nodemask (to not to be cleared once set and survive all further allocation and freeing. I modify PAGE_FLAGS_CHECK_AT_PREP to

How does OS kernel get notified when memory is accessed?

As far as I know, OS kernel maintains the translation from virtual address to physical address, and the userspace program uses virtual address, the CPU uses physical address. Since all machine codes are executed by CPU, how does OS kernel know a memory access instruction is taken, and translate the virtual address to physical address? CPU can execute a syscall

Where is the memusage command in Ubuntu? [closed]

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