On Fri, 2025-10-17 at 14:11 +0200, Gero wrote: > Dear experts, > > thanks a lot for your work and commitment on the Debian system. I'm > using Debian for years and I am generally very pleased with it. :-) > > With my company we do numerical simulations and recently did some > benchmarking tests on new AMD EPYC 9334 processors that showed a > significant performance loss of a current Debian system compared to an > older Red Hat or Rocky Linux. We could narrow that down to the following > finding: > > Running these commands: > > cd /dev/shm > echo 3 > /proc/sys/vm/drop_caches > fio --name=random-write --ioengine=posixaio --rw=randwrite --bs=4k > --numjobs=1 --size=4g --iodepth=1 --runtime=60 --time_based --end_fsync=1 [...] > I would like to know if you have an explanation or an idea. I think for this specific test, the explanation is "this is a stupid I/O pattern that no-one optimises for". Using AIO with a depth of 1 is effectively doing synchronous I/O in a less efficient way. Added to that, POSIX AIO was never that efficient on Linux, and the upstream developers seem to have more-or-less given up on it in favour of io_uring. > And I wonder > if you would be interested in investigating the issue any further. Or if > you have a suggestion who I might address preferably. If you can also see a regression for io_uring and a more sensible I/O depth then this would probably be interesting for the upstream developers, Ben. -- Ben Hutchings Computers are not intelligent. They only think they are.
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