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author | Rafał Miłecki <rafal@milecki.pl> | 2022-07-03 13:22:00 +0200 |
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committer | Rafał Miłecki <rafal@milecki.pl> | 2022-07-03 13:59:12 +0200 |
commit | abc5b28db164dc2d807750cb2baae91e288c84a9 (patch) | |
tree | 9a5a39ef0ea23f0089d9da2d1c5ad6b009258343 /config/check-uname.sh | |
parent | 24eee4b2443d75f51a91fd321c68705a6f376ccc (diff) | |
download | upstream-abc5b28db164dc2d807750cb2baae91e288c84a9.tar.gz upstream-abc5b28db164dc2d807750cb2baae91e288c84a9.tar.bz2 upstream-abc5b28db164dc2d807750cb2baae91e288c84a9.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>
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