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| author | Rafał Miłecki <rafal@milecki.pl> | 2022-07-03 13:22:00 +0200 |
|---|---|---|
| committer | Rafał Miłecki <rafal@milecki.pl> | 2022-07-08 16:18:25 +0200 |
| commit | b54ef39e0b910a4b8eaca0497fe9b63e8392262a (patch) | |
| tree | b9ed5ba53325ebdfc918af0f5b3d62d6b94f6d0e | |
| parent | a50f5b3fb2024fe00f726dff2093a83410bd3c8d (diff) | |
| download | upstream-b54ef39e0b910a4b8eaca0497fe9b63e8392262a.tar.gz upstream-b54ef39e0b910a4b8eaca0497fe9b63e8392262a.tar.bz2 upstream-b54ef39e0b910a4b8eaca0497fe9b63e8392262a.zip | |
bcm53xx: use -falign-functions=32 for kernel compilation
Northstar SoCs have pretty small CPU caches and their performance is
heavily affected by cache hits & misses. It means that all kind of
random code changes can affect performance as they often reorganize
(change alignment & possibly reorder) kernel symbols.
It was discussed in ARM / net mailinglists:
1. ARM router NAT performance affected by random/unrelated commits [1] [2]
2. Optimizing kernel compilation / alignments for network performance [3] [4]
It seems that -falign-functions can be used as a partial workaround. It
doesn't solve all cases (e.g. documented watchdog one [5]) but it surely
helps with many of them.
A complete long term solution may be PGO (profile-guided optimization)
but it isn't available at this point.
[1] https://lkml.org/lkml/2019/5/21/349
[2] https://www.spinics.net/lists/linux-block/msg40624.html
[3] https://lore.kernel.org/linux-arm-kernel/066fc320-dc04-11a4-476e-b0d11f3b17e6@gmail.com/T/
[4] https://www.spinics.net/lists/netdev/msg816103.html
[5] http://lists.openwrt.org/pipermail/openwrt-devel/2022-July/038989.html
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit abc5b28db164dc2d807750cb2baae91e288c84a9)
| -rw-r--r-- | config/Config-devel.in | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/config/Config-devel.in b/config/Config-devel.in index a068f694e5..87f9157106 100644 --- a/config/Config-devel.in +++ b/config/Config-devel.in @@ -76,6 +76,7 @@ menuconfig DEVEL config KERNEL_CFLAGS string "Kernel extra CFLAGS" if DEVEL + default "-falign-functions=32" if TARGET_bcm53xx default "" config EXTERNAL_KERNEL_TREE |