CODEWITHSUNDEEP
windowscachingwindows-10compression7zip
shind
shind

Reputation: 1

7z compression slows down sharply after triggering the caching mechanism

Phenomenon

I am using 7z compressing software and I want to compress a virtual machine folder (14 GB, 49 files) into a zip file at the same folder. I just keep the default options of "zip format" in 7z, and when I start to compress, the speed first reaches about 170 MB/s, and then drops to about 20 MB/s in the end, which really confuses me.

Configuration

Hardware configuration is:

  1. CPU: Intel i9-13900HX;
  2. Memory: Samsung DDR5 5600MHz 16 GB×2;
  3. Disk: KIOXIA SSD KXG80ZNV1T02 1TB (OS); Predator SSD GM7 2TB (where the compression performs).

Software configuration is:

  1. OS: Windows 11 22H2;
  2. 7zip, version 22.01 x64. 7z settings for this compressing process are shown in the picture below: 7z settings

Analysis

Here I present screenshots during the compressing process for you to check the problem.

  1. The compressing speed drop screenshot. pic: compressing speed when compressing starts pic: compressing speed drops
  2. When the compressing speed drops, CPU usage drops accordingly, which implies CPU is not the bottleneck of slow compressing (The window of 7z is always kept at the front to prevent big and small core scheduling problems on win11&13th CPUs). pic: CPU usage drops
  3. The gradual increase of memory cache. Compression speed is very fast when used memory grows, and the compression speed immediately drops when memory cache starts to grow. pic: used memory increases

Question

  1. There is obviously enough memory available, but why is the memory used by 7zip immediately written to the cache after a slight increase, which seriously affects performance?

  2. Whose action is it to write the increasing memory to the cache? Windows or 7zip? Is the cache on the OS disk so slow?

  3. In order to solve problem 1, is there any GUI method for streaming compression which does not use much memory for temporary file storage, thus may not able to trigger the slow caching mechanism?

This test is also performed on another laptop with Windows 10 and 7zip installed. The result is the same.

Upvotes: 0

Views: 161

Answers (0)

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