Fix stack usage on parisc & improve code size bloat
This PR contains 3 commits:
1. Fixes a minor unused variable warning reported by Kernel test robot [0].
2. Improves the reported code bloat (-88KB / 374KB) [1] by outlining
some functions that are unlikely to be used in performance sensitive
workloads.
3. Fixes the reported excess stack usage on parisc [2] by removing -O3
from zstd's compilation flags. -O3 triggered bugs in the hppa-linux-gnu
gcc-8 compiler. -O2 performance is acceptable: neutral compression,
about -1% decompression speed. We also reduce code bloat
(-105KB / 374KB).
After this commit our code bloat is cut from 374KB to 105KB with gcc-11.
If we wanted to cut the remaining 105KB we'd likely have to trade
signicant performance, so I want to say that this is enough for now.
We should be able to get further gains without sacrificing speed, but
that will take some significant optimization effort, and isn't suitable
for a quick fix. I've opened an upstream issue [3] to track the code size,
and try to avoid future regressions, and improve it in the long term.
[0] https://lore.kernel.org/linux-mm/202111120312.833wII4i-lkp@intel.com/T/
[1] https://lkml.org/lkml/2021/11/15/710
[2] https://lkml.org/lkml/2021/11/14/189
[3] https://github.com/facebook/zstd/issues/2867
Link: https://lore.kernel.org/r/20211117014949.1169186-1-nickrterrell@gmail.com/
Link: https://lore.kernel.org/r/20211117201459.1194876-1-nickrterrell@gmail.com/
Signed-off-by: Nick Terrell <terrelln@fb.com>
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Merge tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux
Pull zstd fixes from Nick Terrell:
"Fix stack usage on parisc & improve code size bloat
This contains three commits:
1. Fixes a minor unused variable warning reported by Kernel test
robot [0].
2. Improves the reported code bloat (-88KB / 374KB) [1] by outlining
some functions that are unlikely to be used in performance
sensitive workloads.
3. Fixes the reported excess stack usage on parisc [2] by removing
-O3 from zstd's compilation flags. -O3 triggered bugs in the
hppa-linux-gnu gcc-8 compiler. -O2 performance is acceptable:
neutral compression, about -1% decompression speed. We also reduce
code bloat (-105KB / 374KB).
After this our code bloat is cut from 374KB to 105KB with gcc-11. If
we wanted to cut the remaining 105KB we'd likely have to trade
signicant performance, so I want to say that this is enough for now.
We should be able to get further gains without sacrificing speed, but
that will take some significant optimization effort, and isn't
suitable for a quick fix. I've opened an upstream issue [3] to track
the code size, and try to avoid future regressions, and improve it in
the long term"
Link: https://lore.kernel.org/linux-mm/202111120312.833wII4i-lkp@intel.com/T/ [0]
Link: https://lkml.org/lkml/2021/11/15/710 [1]
Link: https://lkml.org/lkml/2021/11/14/189 [2]
Link: https://github.com/facebook/zstd/issues/2867 [3]
Link: https://lore.kernel.org/r/20211117014949.1169186-1-nickrterrell@gmail.com/
Link: https://lore.kernel.org/r/20211117201459.1194876-1-nickrterrell@gmail.com/
* tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux:
lib: zstd: Don't add -O3 to cflags
lib: zstd: Don't inline functions in zstd_opt.c
lib: zstd: Fix unused variable warning
