On 2015-06-04 11:56, Markos Chandras wrote: > This commit introduces BPF ASM helpers for MIPS and MIPS64 kernels. > The purpose of this patch is to twofold: > > 1) We are now able to handle negative offsets instead of either > falling back to the interpreter or to simply not do anything and > bail out. > > 2) Optimize reads from the packet header instead of calling the C > helpers > > Because of this patch, we are now able to get rid of quite a bit of > code in the JIT generation process by using MIPS optimized assembly > code. The new assembly code makes the test_bpf testsuite happy with > all 60 test passing successfully compared to the previous > implementation where 2 tests were failing. > Doing some basic analysis in the results between the old > implementation and the new one we can obtain the following > summary running current mainline on an ER8 board (+/- 30us delta is > ignored to prevent noise from kernel scheduling or IRQ latencies): > > Summary: 22 tests are faster, 7 are slower and 47 saw no improvement > > with the most notable improvement being the tcpdump tests. The 7 tests > that seem to be a bit slower is because they all follow the slow path > (bpf_internal_load_pointer_neg_helper) which is meant to be slow so > that's not a problem. > > Cc: netdev@xxxxxxxxxxxxxxx > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> > Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx> > Cc: Daniel Borkmann <dborkman@xxxxxxxxxx> > Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx > Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx> > --- > I have uploaded the script and the bpf result files in my LMO webspace > in case you want to have a look. I didn't paste them in here because they > are nearly 200 lines. Simply download all 3 files and run './bpf_analysis.py' This patch relies on R2 instructions, and thus the Linux kernel fails to build when targetting non-R2 CPUs. See for example: https://buildd.debian.org/status/fetch.php?pkg=linux&arch=mipsel&ver=4.2%7Erc6-1%7Eexp1&stamp=1439480000 -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@xxxxxxxxxxx http://www.aurel32.net
