linux-kernel - Re: [PATCH 17/17] vsprintf: rework bitmap_list

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Message-ID: <YRvlUO87e7czAico@yury-ThinkPad>
Date:   Tue, 17 Aug 2021 09:35:28 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
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Subject: Re: [PATCH 17/17] vsprintf: rework bitmap_list_string

On Sun, Aug 15, 2021 at 02:09:45PM +0300, Andy Shevchenko wrote:
> On Sun, Aug 15, 2021 at 12:21 AM Yury Norov <yury.norov@...il.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 in the
> > bitmap.  We can do better by detecting ranges of set bits.
> >
> > In my environment, before/after is 943008/31008 ns.
> 
> I would add a couple of words, maybe in parentheses, to describe what
> your environment is.
> 
> ...
> 
> > +               buf = number(++buf, end, rtop - 1, default_dec_spec);
> 
> ++buf is a bit confusing here. Since you will rewrite the buf value
> anyway, I would write the parameter as buf + 1.

Agree, it's sloppy. I'll  send the patch by tomorrow.