Messages in this thread | | | Date | Thu, 15 Jul 2021 08:50:21 -0700 | From | Yury Norov <> | Subject | Re: [PATCH 2/2] bitmap: introduce for_each_set_bitrange |
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On Fri, Jul 09, 2021 at 09:59:50AM -0400, Steven Rostedt wrote: > On Thu, 8 Jul 2021 20:45:19 -0700 > Yury Norov <yury.norov@gmail.com> wrote: > > > bitmap_list_string() is very ineffective when printing bitmaps with long > > ranges of set bits because it calls find_next_bit for each bit. We can do > > better by detecting ranges of set bits. > > > > This patch introduces a macro for_each_set_bitrange and uses it in > > bitmap_list_string(). In my environment, before/after is 943008/31008 ns. > > > > Signed-off-by: Yury Norov <yury.norov@gmail.com> > > --- > > include/linux/find.h | 7 +++++++ > > lib/vsprintf.c | 40 ++++++++++++++++------------------------ > > 2 files changed, 23 insertions(+), 24 deletions(-) > > > > diff --git a/include/linux/find.h b/include/linux/find.h > > index ae9ed52b52b8..1a5ed45dc81b 100644 > > --- a/include/linux/find.h > > +++ b/include/linux/find.h > > @@ -301,6 +301,13 @@ unsigned long find_next_bit_le(const void *addr, unsigned > > (bit) < (size); \ > > (bit) = find_next_zero_bit((addr), (size), (bit) + 1)) > > > > +#define for_each_set_bitrange(b, e, addr, size) \ > > The above needs a kerneldoc header.
OK.
> > > + for ((b) = find_next_bit((addr), (size), 0), \ > > + (e) = find_next_zero_bit((addr), (size), (b) + 1); \ > > + (b) < (size); \ > > + (b) = find_next_bit((addr), (size), (e) + 1), \ > > + (e) = find_next_zero_bit((addr), (size), (b) + 1)) > > + > > /** > > * for_each_set_clump8 - iterate over bitmap for each 8-bit clump with set bits > > * @start: bit offset to start search and to store the current iteration offset > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > > index 87acf66f0e4c..1ee54dace71e 100644 > > --- a/lib/vsprintf.c > > +++ b/lib/vsprintf.c > > @@ -1240,38 +1240,30 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap, > > struct printf_spec spec, const char *fmt) > > { > > int nr_bits = max_t(int, spec.field_width, 0); > > - /* current bit is 'cur', most recently seen range is [rbot, rtop] */ > > - int cur, rbot, rtop; > > - bool first = true; > > + char *start = buf; > > + int b, e; > > > > if (check_pointer(&buf, end, bitmap, spec)) > > return buf; > > > > - rbot = cur = find_first_bit(bitmap, nr_bits); > > - while (cur < nr_bits) { > > - rtop = cur; > > - cur = find_next_bit(bitmap, nr_bits, cur + 1); > > - if (cur < nr_bits && cur <= rtop + 1) > > - continue; > > + for_each_set_bitrange(b, e, bitmap, nr_bits) { > > + buf = number(buf, end, b, default_dec_spec); > > + if (e == b + 1) > > + goto put_comma; > > Using a goto to skip a few lines instead of just having the reverse > conditional is rather sloppy IMO. > > if (e != b + 1) { > if (buf < end) > *buf = '-'; > buf++; > buf = number(buf, end, e - 1, default_dec_spec); > } > > Is much clearer.
I don't think it's clearer, but as you wish.
> > > > - if (!first) { > > - if (buf < end) > > - *buf = ','; > > - buf++; > > - } > > - first = false; > > + if (buf < end) > > + *buf = '-'; > > > > - buf = number(buf, end, rbot, default_dec_spec); > > - if (rbot < rtop) { > > - if (buf < end) > > - *buf = '-'; > > - buf++; > > + buf = number(++buf, end, e - 1, default_dec_spec); > > +put_comma: > > + if (buf < end) > > + *buf = ','; > > + buf++; > > + } > > > > - buf = number(buf, end, rtop, default_dec_spec); > > - } > > + if (buf > start) > > + buf--; > > If the above is to undo the last comma, please put back the first logic. > > -- Steve
You're asking me to move part of the logic inside the loop which generally should be avoided. Is there any particular reason to do this?
> > > > > - rbot = cur; > > - } > > return buf; > > } > >
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