ATGC Could Come In Linux 5.10 For F2FS, Much Faster Decompression Speeds Too

Written by Michael Larabel in Linux Storage on 23 August 2020 at 07:10 AM EDT. 9 Comments
We previously reported on F2FS "ATGC" functionality for increasing the garbage collection efficiency for the Flash-Friendly File-System. Those patches are now queued up in F2FS' "dev" branch meaning we could see the functionality in place for Linux 5.10.

F2FS Age Threshold based Garbage Collection is for enhancing the effectiveness and efficiency of the background GC process for the file-system by evaluating older candidates first based on a configurable age threshold.

Huawei engineers who devised the F2FS ATGC implementation found that the garbage collection calls dropped from around 220 to 76 and the data block movement dropped in the range of 41k to 12k.

This improvement for the F2FS garbage collector is now in the F2FS dev branch. for post-5.9 kernel material. Unless any issues come up with it during testing, we should be seeing it in Linux 5.10 towards the end of the year.

Also in the dev branch is this patch by Google engineers for changing the virtual mapping handling for compression pages. On the Android Pixel 3 prior to this patch the decompression speed was around 137M/s while with this patch it jumps all the way to 503M/s. A huge win for decompression speed by changing around a few dozen lines of code that basically change vmap() usage to vm_map_ram() calls. This virtual mapping rework even puts the speed now to be greater than the ~480M/s performance without compression.
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