lkml.org 
[lkml]   [2006]   [Dec]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: replace "memset(...,0,PAGE_SIZE)" calls with "clear_page()"?
On Sat, 30 Dec 2006, Arjan van de Ven wrote:

> rday wrote:

> > ... most of the definitions of the clear_page() macro are simply
> > invocations of memset(). see for yourself:

> *MOST*. Not all.

i did notice that. while the majority of the architectures simply
define clear_page() as a macro calling memset(ptr, 0, PAGE_SIZE), the
rest will implement it in assembler code for whatever reason. (i'm
assuming that *every* architecture *must* define clear_page() one way
or the other, is that correct? that would seem fairly obvious, but
i just want to make sure i'm not missing anything obvious.)

> clear_page() is supposed to be for full real pages only... for
> example it allows the architecture to optimize for alignment, cache
> aliasing etc etc.

fair enough. *technically*, not every call of the form
"memset(ptr,0,PAGE_SIZE)" necessarily represents an address that's on
a page boundary. but, *realistically*, i'm guessing most of them do.
just grabbing a random example from some grep output:

arch/sh/mm/init.c:
...
/* clear the zero-page */
memset(empty_zero_page, 0, PAGE_SIZE);
...

my only point here is that, given that every architecture needs to
supply some kind of definition of a "clear_page()" routine, one would
think that *lots* of those memset() calls could reasonably be
rewritten as a clear_page() call for improved readibility, no?

and there are a *lot* of memset() calls like that.

rday
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-12-31 00:13    [W:0.781 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site