diff --git a/README.md b/README.md index 6227d65..f979809 100644 --- a/README.md +++ b/README.md @@ -9,7 +9,7 @@ Run one command, get a QEMU Buildroot BusyBox virtual machine built from source cd kernel_module ./make-host.sh -If the compilation of any of the C files fails (because of kernel or toolchain differences that we don't control on the host), just rename it to remove the `.c` extension and try again: +If the compilation of any of the C files fails, e.g. because of kernel or toolchain differences that we don't control on the host, just rename it to remove the `.c` extension and try again: mv broken.c broken.c~ ./build_host @@ -601,6 +601,8 @@ Parameter notes: Without it, the bulk of the time seems to be spent in setting up the network with `ifup` that gets called from `/etc/init.d/S40network` from the default Buildroot BusyBox setup. + And it becomes even worse if you try to `-net none` as recommended in the 2.7 `replay.txt` docs, because then `ifup` waits for 15 seconds before giving up as per `/etc/network/interfaces` line `wait-delay 15`. + This works because we have already done the following with QEMU: - `./configure --enable-trace-backends=simple`. This logs in a binary format to the trace file. @@ -618,6 +620,8 @@ Possible improvements: - - + `CONFIG_NET=n` did not significantly reduce instruction, so maybe replacing `init` is enough. + - logging with the default backend `log` greatly slows down the CPU, and in particular leads to this during kernel boot: All QSes seen, last rcu_sched kthread activity 5252 (4294901421-4294896169), jiffies_till_next_fqs=1, root ->qsmask 0x0 diff --git a/kernel_config_fragment b/kernel_config_fragment index 5bfc604..83e9381 100644 --- a/kernel_config_fragment +++ b/kernel_config_fragment @@ -53,6 +53,10 @@ CONFIG_SCHED_TRACER=y CONFIG_STACK_TRACER=y CONFIG_TRACER_SNAPSHOT=y +# Will everything blow up? +# https://superuser.com/questions/684005/how-does-one-permanently-disable-gnu-linux-networking/1255015#1255015 +#CONFIG_NET=n + ## x86 # https://stackoverflow.com/questions/20069620/print-kernels-page-table-entries