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From: Matthew Wilcox <willy@infradead.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, pmladek@suse.com,
	rostedt@goodmis.org, sergey.senozhatsky@gmail.com,
	andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk
Subject: Re: [PATCH 03/15] print_integer: new and improved way of printing integers
Date: Tue, 21 Apr 2020 09:59:48 -0700	[thread overview]
Message-ID: <20200421165948.GO5820@bombadil.infradead.org> (raw)
In-Reply-To: <20200420205743.19964-3-adobriyan@gmail.com>

On Mon, Apr 20, 2020 at 11:57:31PM +0300, Alexey Dobriyan wrote:
> 1) memcpy is done in forward direction
> 	it can be done backwards but nobody does that,

If you're determined to do this, then use memmove() which actually
guarantees to work with overlapping ranges.  Don't rely on non-guaranteed
behaviour of current implementations of memcpy().  Did you really check
the two dozen assembly implementations of memcpy() in the kernel?

> 2) digits can be extracted in a very simple loop which costs only
> 	1 multiplication and shift (division by constant is not division)

> +noinline
> +char *_print_integer_u32(char *p, u32 x)
> +{
> +	do {
> +		*--p = '0' + (x % 10);
> +	} while (x /= 10);
> +	return p;
> +}

Why not do two digits at a time like put_dec() does?


  parent reply	other threads:[~2020-04-21 16:59 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-20 20:57 [PATCH 01/15] sched: make nr_running() return "unsigned int" Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 02/15] sched: make nr_iowait_cpu() " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 03/15] print_integer: new and improved way of printing integers Alexey Dobriyan
2020-04-20 21:19   ` Andy Shevchenko
2020-04-20 21:27     ` Andy Shevchenko
2020-04-21  1:54       ` Steven Rostedt
2020-04-21 16:49         ` Alexey Dobriyan
2020-04-21 21:08           ` Steven Rostedt
2020-04-23  3:42           ` Sergey Senozhatsky
2020-04-21 16:31     ` Alexey Dobriyan
2020-04-21 16:59   ` Matthew Wilcox [this message]
2020-04-20 20:57 ` [PATCH 04/15] print_integer, proc: rewrite /proc/self via print_integer() Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 05/15] print_integer, proc: rewrite /proc/thread-self " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 06/15] print_integer, proc: rewrite /proc/loadavg " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 07/15] print_integer, proc: rewrite /proc/stat " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 08/15] print_integer, proc: rewrite /proc/uptime " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 09/15] proc: s/p/tsk/ Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 10/15] print_integer, proc: rewrite /proc/*/fd via print_integer() Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 11/15] print_integer, proc: rewrite /proc/*/stat " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 12/15] print_integer, proc: rewrite /proc/*/statm " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 13/15] print_integer, printf: rewrite num_to_str() " Alexey Dobriyan
2020-04-20 20:57 ` [PATCH 14/15] print_integer, printf: rewrite the rest of lib/vsprintf.c " Alexey Dobriyan
2020-04-21  2:01   ` Steven Rostedt
2020-04-20 20:57 ` [PATCH 15/15] print_integer, proc: rewrite /proc/meminfo " Alexey Dobriyan
2020-04-20 21:05 ` [PATCH 01/15] sched: make nr_running() return "unsigned int" Matthew Wilcox
2020-04-21 17:06   ` Alexey Dobriyan

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