4 ms·

https://learn.microsoft.com/en-us/sysinternals/downloads/vmmap https://learn.microsoft.com/en-us/sysinternals/downloads/vmm... for an empty sublime text window

by pjc50 7mo ago

https://learn.microsoft.com/en-us/sysinternals/downloads/vmmap https://learn.microsoft.com/en-us/sysinternals/downloads/vmm... for an empty sublime text window gives me: - 100MB 'image' (ie executable code; the executable itself plus all the OS libraries loaded.) - 40MB heap - 50MB "mapped file", mostly fonts opened with mmap() or the windows equivalent - 45MB stack (each thread gets 2MB) - 40MB "shareable" (no idea) - 5MB "unusable" (appears to be address space that's not usable because of fragmentation, not actual RAM) Generally if something's using a lot of RAM, the answer will be bitmaps of various sorts: draw buffers, decompressed textures, fonts, other graphical assets, and so on. In this case it's just allocated but not yet used heap+stacks, plus 100MB for the code. Edit: I may be underestimating the role of binary code size. Visual Studio "devenv.exe" is sitting at 2GB of 'image'. Zoom is 500MB. VSCode is 300MB. Much of which are app-specific, not just Windows DLLs.

Capricorn2481 7mo ago
But I have sublime text open with a hundred files and it's using 12mb.
- pjc50 7mo ago
  And how does that breakdown in vmmap? I'm guessing that's working set vs. the whole virtual memory allocation (which is definitely always an overestimate and not the same as RAM)
  - wild_egg 7mo ago
    Virtual memory doesn't matter at all. It's virtual. You can take 2TB of address space, use 5MB of it, and nothing on the system cares.
muskstinks 7mo ago
Tx for the breakdown. I will play around with it later on my windows machine. But isn't it crazy how we throw out so much memory just because of random buffers? It feels wrong to me
- pjc50 7mo ago
  As pointed out below, quite a lot of that isn't in RAM - see "working set". There's a common noob complaint about "Linux using all my RAM!" where people are confused about the headline free/buffers numbers. If there's a reasonable chance data could be used again soon it's better to leave it in RAM; if the RAM is needed for something else, the current contents will get paged out. Having a chunk of RAM be genuinely unallocated to anything is doing nothing for you.
  - fluoridation 7mo ago
    Nitpick: What you're describing is the disk cache. If a process requests more memory than is free, the OS will not page out pages used for the cache, it will simply either release them (if they're on the read cache) or flush them (if they're on the write cache).
  - HappMacDonald 7mo ago
    Of course it's doing something for you. Room to defrag other areas of RAM, room to load something new without moving something else out of the way first. Your perspective sounds like the concept that space in a room does nothing for you until/unless you cram it full of hoarded items.
    - Melatonic 7mo ago
      If we're talking about a storage locker that's instantly reconfigurable then it is probably better to be approximately filling it. Why would anyone buy a locker 5x the size of their needs ?
- groby_b 7mo ago
  If you didn't have the "random" buffers, you'd complain how slow it is. Syntax highlighting? Needs a boatload of caching to be efficient. Code search? Hey, you want a cached code index. Plugins? Gotta run your python code somewhere. Run vi/nano/micro/joe - they're optimizing for memory to some extent. vi clocks in at under 8 MB. You're giving up a lot of "nice" things to get there.
wat10000 7mo ago
Turning these numbers into "memory consumption" gets complicated to the point of being intractable. The portions that are allocated but not yet used might just be page table entries with no backing memory, making them free. Except for the memory tracking the page table entries. Almost free.... A lot of "image" will be mmapped and clean. Anything you don't actually use from that will be similarly freeish. Anything that's constantly needed will use memory. Except if it's mapped into multiple processes, then it's needed but responsibility is spread out. How do you count an app's memory usage when there's a big chunk of code that needs to sit in RAM as long as any of a dozen processes are running? How do you count code that might be used sometime in the next few minutes or might not be depending on what the user does?
- gmueckl 7mo ago
  This assumes that executable code pages can be shared between processes. I'm skeptical that this is still a notable optimization on modern systems because dynamic linking writes to executable memory to perform relocations in the loaded code. So this would counteract copy on write. And at least with ASLR, the result should be different for each process anyway.
  - cataphract 7mo ago
    ld writes to the GOT. The executable segment where .text lives is not written to (it's position independent code in dynamic libraries). ASLR is not an obstacle -- the same exact code can be mapped into different base addresses in different processes, so they can be backed by the same actual memory.
    - manwe150 7mo ago
      That’s true on most systems (modern or not), but actually never been true on Windows due to PE/COFF format limitations. But also, that system doesn’t/can’t do effective ASLR because of the binary slide being part of the object file spec.
    - gmueckl 7mo ago

by pjc50 7mo ago

Capricorn2481 7mo ago

But I have sublime text open with a hundred files and it's using 12mb.

pjc50 7mo ago
And how does that breakdown in vmmap? I'm guessing that's working set vs. the whole virtual memory allocation (which is definitely always an overestimate and not the same as RAM)
- wild_egg 7mo ago
  Virtual memory doesn't matter at all. It's virtual. You can take 2TB of address space, use 5MB of it, and nothing on the system cares.

muskstinks 7mo ago

Tx for the breakdown. I will play around with it later on my windows machine. But isn't it crazy how we throw out so much memory just because of random buffers? It feels wrong to me

pjc50 7mo ago
As pointed out below, quite a lot of that isn't in RAM - see "working set". There's a common noob complaint about "Linux using all my RAM!" where people are confused about the headline free/buffers numbers. If there's a reasonable chance data could be used again soon it's better to leave it in RAM; if the RAM is needed for something else, the current contents will get paged out. Having a chunk of RAM be genuinely unallocated to anything is doing nothing for you.
- fluoridation 7mo ago
  Nitpick: What you're describing is the disk cache. If a process requests more memory than is free, the OS will not page out pages used for the cache, it will simply either release them (if they're on the read cache) or flush them (if they're on the write cache).
- HappMacDonald 7mo ago
  Of course it's doing something for you. Room to defrag other areas of RAM, room to load something new without moving something else out of the way first. Your perspective sounds like the concept that space in a room does nothing for you until/unless you cram it full of hoarded items.
  - Melatonic 7mo ago
    If we're talking about a storage locker that's instantly reconfigurable then it is probably better to be approximately filling it. Why would anyone buy a locker 5x the size of their needs ?
groby_b 7mo ago
If you didn't have the "random" buffers, you'd complain how slow it is. Syntax highlighting? Needs a boatload of caching to be efficient. Code search? Hey, you want a cached code index. Plugins? Gotta run your python code somewhere. Run vi/nano/micro/joe - they're optimizing for memory to some extent. vi clocks in at under 8 MB. You're giving up a lot of "nice" things to get there.

wat10000 7mo ago

Turning these numbers into "memory consumption" gets complicated to the point of being intractable. The portions that are allocated but not yet used might just be page table entries with no backing memory, making them free. Except for the memory tracking the page table entries. Almost free.... A lot of "image" will be mmapped and clean. Anything you don't actually use from that will be similarly freeish. Anything that's constantly needed will use memory. Except if it's mapped into multiple processes, then it's needed but responsibility is spread out. How do you count an app's memory usage when there's a big chunk of code that needs to sit in RAM as long as any of a dozen processes are running? How do you count code that might be used sometime in the next few minutes or might not be depending on what the user does?

gmueckl 7mo ago
This assumes that executable code pages can be shared between processes. I'm skeptical that this is still a notable optimization on modern systems because dynamic linking writes to executable memory to perform relocations in the loaded code. So this would counteract copy on write. And at least with ASLR, the result should be different for each process anyway.
- cataphract 7mo ago
  ld writes to the GOT. The executable segment where .text lives is not written to (it's position independent code in dynamic libraries). ASLR is not an obstacle -- the same exact code can be mapped into different base addresses in different processes, so they can be backed by the same actual memory.
  - manwe150 7mo ago
    That’s true on most systems (modern or not), but actually never been true on Windows due to PE/COFF format limitations. But also, that system doesn’t/can’t do effective ASLR because of the binary slide being part of the object file spec.
  - gmueckl 7mo ago