3rd-party/linux-kernel-module-cheat
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CONFIG_NET=n commented out

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Ciro Santilli
2017-10-01 11:07:48 +01:00
parent f96d4d55c9
commit 0e486fd65b
2 changed files with 9 additions and 1 deletions
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6
README.md
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@@ -9,7 +9,7 @@ Run one command, get a QEMU Buildroot BusyBox virtual machine built from source
cd kernel_module cd kernel_module
./make-host.sh ./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~ mv broken.c broken.c~
./build_host ./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. 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: 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. - `./configure --enable-trace-backends=simple`. This logs in a binary format to the trace file.
@@ -618,6 +620,8 @@ Possible improvements:
- <https://superuser.com/questions/181254/how-do-you-boot-linux-with-networking-disabled> - <https://superuser.com/questions/181254/how-do-you-boot-linux-with-networking-disabled>
- <https://superuser.com/questions/684005/how-does-one-permanently-disable-gnu-linux-networking/1255015#1255015> - <https://superuser.com/questions/684005/how-does-one-permanently-disable-gnu-linux-networking/1255015#1255015>
`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: - 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 All QSes seen, last rcu_sched kthread activity 5252 (4294901421-4294896169), jiffies_till_next_fqs=1, root ->qsmask 0x0

4
kernel_config_fragment
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@@ -53,6 +53,10 @@ CONFIG_SCHED_TRACER=y
CONFIG_STACK_TRACER=y CONFIG_STACK_TRACER=y
CONFIG_TRACER_SNAPSHOT=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 ## x86
# https://stackoverflow.com/questions/20069620/print-kernels-page-table-entries # https://stackoverflow.com/questions/20069620/print-kernels-page-table-entries