(cache)How to read data from an ext4 with higher block size than 4K on x86_64?

exerceo · 09-05-2025, 06:59 PM

ext4 supports a block size of up to 64K, but Linux can only read ext4 file systems with block sizes not exceeding the CPU page size, which is 4K for x86_64 (getconf PAGESIZE).

Is there any way to read data from a higher block size ext4? I know, it will probably not have good performance, but still. mkfs.etxt4 can creade a 64K block file system on any system.

teckk · 09-06-2025, 12:10 PM

From what I have read, you can make a ext4 file system with a greater than 4K block size, but you'll need to edit/recompile your kernel to read it on a linux machine.

xlfs-0.2 · 09-18-2025, 01:48 AM

that may not work better and depends on chip internals and how linux uses them

making large blocks means if you read a small file you take a penalty. this includes software that "reads allot of data" with internal block sizes sized to not over-run internal software buffers

back to kernel land: the disk has a built-in 8M or what cache and linux caches. what you'd save probably will disappoint you unless you "edit movies allot and really need large block sizes" at any cost to the rest of the system

xlfs-0.2 · 09-18-2025, 01:49 AM

nothing stops software from utilizing hardware to read long blocks per say

but you are talking about forcing a solution system wide i assume