Messages in this thread | | | Date | Wed, 21 Sep 2022 08:40:00 -0700 | From | Yury Norov <> | Subject | Re: [PATCH v4 0/4] lib: optimize find_bit() functions |
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If no other comments, I'll address Andy's comments on formatting and move it in bitmap-for-next.
Thanks, Yury
On Wed, Sep 14, 2022 at 07:07:26PM -0700, Yury Norov wrote: > In the recent discussion, it was noticed that find_next_bit() functions may > be improved by adding wrappers around common __find_next_bit() in .c file. > > As suggested by Linus, I tried the meta-programming trick with the > EXPRESSION macro, which is passed from wrapper into find_bit() > helpers: > > #define BIT_FIND_BODY(addr, size, start, EXPRESSION) \ > BIT_FIND_SETUP(addr, size, start) \ > BIT_FIND_FIRST_WORD(addr, size, start, EXPRESSION) \ > BIT_WORD_LOOP(addr, size, idx, val, EXPRESSION) \ > return size; \ > found: BIT_WORD_SWAB(val); \ > return min((idx)*BITS_PER_LONG + __ffs(val), size) > > unsigned long _find_next_and_bit(const unsigned long *addr1, > const unsigned long *addr2, > unsigned long size, > unsigned long start) > { BIT_FIND_BODY(addr, size, start, addr1[idx] & addr2[idx]); } > > I appreciated the potential of how the EXPRESSION works, but I don't like > that the resulting macro is constructed from pieces because it makes it > harder to understand what happens behind the ifdefery. Checkpatch isn't > happy as well because the final macro contains 'return' statement; and I > would agree that it's better to avoid it. > > I spun the idea one more time, trying to make FIND helper a more or > less standard looking macro. > > This new approach saves 10-11K of Image size, and is 15% faster in the > performance benchmark. See the 3rd patch for some statistics. > > v1: https://lore.kernel.org/all/20220728161208.865420-2-yury.norov@gmail.com/T/ > v2: https://lore.kernel.org/lkml/YwaXvphVpy5A7fSs@yury-laptop/t/ > v3: https://lore.kernel.org/all/xhsmhedwnb15r.mognet@vschneid.remote.csb/T/ > v4: > - fix for-loop break condition in FIND_NEXT_BIT; > - add review tags from Valentin Schneider. > > Yury Norov (4): > lib/find_bit: introduce FIND_FIRST_BIT() macro > lib/find_bit: create find_first_zero_bit_le() > lib/find_bit: optimize find_next_bit() functions > tools: sync find_bit() implementation > > include/linux/find.h | 46 +++++++--- > lib/find_bit.c | 178 ++++++++++++++++++++++--------------- > tools/include/linux/find.h | 61 +++---------- > tools/lib/find_bit.c | 149 ++++++++++++++----------------- > 4 files changed, 220 insertions(+), 214 deletions(-) > > -- > 2.34.1
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