jrtore.blogg.se - Cpuinfo rnrn field explained

#CPUINFO RNRN FIELD EXPLAINED FREE#

If this is omitted, all processors are displayed.

PageTables: amount of memory dedicated to the lowest level of page tables.The !cpuinfo extension displays detailed information about the target computer's CPU.

The Committed_AS is a guesstimate of how much RAM/swap you would need worst-case. While it normally is shared between processes. Other cases might include when you mmap a file that’s shared only when you write to it and you get a private copy of that data. So you sort of take a mortgage and hope the bank doesn’t go bust. Only when you start USING that malloc memory you will get real memory on demand, and just as much as you use. That means, say you do a 1GB malloc, nothing happens,really. Normally the kernel will overcommit memory.

Committed_AS: An estimate of how much RAM you would need to make a 99.99% guarantee that there never is OOM (out of memory) for this workload.

Mapped: files which have been mapped, such as libraries.

Writeback: Memory which is actively being written back to the disk.

Dirty: Memory which is waiting to get written back to the disk.

Memory which has been evicted from RAM, and is temporarily on the disk

SwapFree: Total amount of swap memory free.

SwapTotal: Total amount of physical swap memory.

All kernel data structures need to go into low memory. This is the memory the kernel can address directly.

#CPUINFO RNRN FIELD EXPLAINED FREE#

LowFree: The amount of free memory of the low memory region.LowTotal: The total amount of non-highmem memory.Kernel uses indirect tricks to access the high memory region. Highmem is all memory above (approx) 860MB of physical RAM. HighTotal: is the total amount of memory in the high region.So you can get more inactive pages than the target because the kernel marks some cache as “more likely to be never used” and lets it cheat in the “last used” order. if you do a long sequential I/O, the kernel assumes you’re not going to use that memory and makes it inactive preventively. A page can also get inactive in a few other ways, e.g. When exceeded, the kernel will not do work to move pages from active to inactive. Inact_target: Just a goal metric the kernel uses for making sure there are enough inactive pages around.The kernel will try to keep some clean stuff around always to have a bit of breathing room. Inact_clean: Assumed to be easily free-able.For instance, if you’re writing logs, it might be better to wait until you have a complete log ready before sending it to disk. They aren’t written to memory too soon in order to keep the I/O down. Example might be files that have not been written to yet. Inact_dirty: Dirty means “might need writing to disk or swap.” Takes more work to free.Active: Memory that has been used more recently and usually not reclaimed unless absolute necessary.The vm checks what is used on a regular basis and moves stuff around. The idea is that if you need memory and some cache needs to be sacrificed for that, you take it from inactive since that’s expected to be not used. VM splits the cache pages into “active” and “inactive” memory. SwapCache: Memory that once was swapped out, is swapped back in but still also is in the swapfile (if memory is needed it doesn’t need to be swapped out AGAIN because it is already in the swapfile.Cached: Memory in the pagecache (diskcache) minus SwapCache, Doesn’t include SwapCached.mostly useless as metric nowadays Relatively temporary storage for raw disk blocks shouldn’t get tremendously large (20MB or so) MemShared: 0 is here for compat reasons but always zero.MemFree: Is sum of LowFree+HighFree (overall stat).physical ram minus a few reserved bits and the kernel binary code)

We will first discuss the high-statistics. Below you find the individual values we will discuss. At the top you see a summary of the most common values people would like to look at. The information comes in the form of both high and low statistics.