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From: Arnaldo Carvalho de Melo <acme-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: jamal <hadi-fAAogVwAN2Kw5LPnMra/2Q@public.gmane.org>
Cc: dwarves-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: Changing the word-size was: Re: eat your own dog food?
Date: Sat, 12 Jan 2008 14:28:08 -0200
Message-ID: <20080112162808.GC23567@ghostprotocols.net> (raw)
In-Reply-To: <20080112155404.GB23567-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>

Em Sat, Jan 12, 2008 at 01:54:04PM -0200, Arnaldo Carvalho de Melo escreveu:
> Em Sat, Jan 12, 2008 at 01:21:09PM -0200, Arnaldo Carvalho de Melo escreveu:
> > Em Thu, Jan 10, 2008 at 04:41:16PM -0500, jamal escreveu:
> > > On Thu, 2008-10-01 at 19:39 -0200, Arnaldo Carvalho de Melo wrote:
> > > 
> > > 
> > > > Working now on unions, etc, have you had the chance of testing this
> > > > patch?
> > > 
> > > I should be able to test it in a couple of hours. If you have the unions
> > > change before then, send me a unified patch - else an incremental
> > > version.
> > 
> > Remove the non-commited patches and do a git-pull, basic work is done,
> > reusing code I had in ctracer to do some simple alignment fixups.
> > 
> > Please let me know about any bugs you may find.
> 
> There are still some problems:
> 
> [acme@doppio pahole]$ build/pahole -C e1000_opt_list \
> /usr/lib/debug/lib/modules/2.6.21-65.el5rt/kernel/drivers/net/e1000/e1000.ko.debug
> 
> struct e1000_opt_list {
> 	int                        i;                    /*     0     4 */
> 
> 	/* XXX 4 bytes hole, try to pack */
> 
> 	char *                     str;                  /*     8     8 */
> 
> 	/* size: 16, cachelines: 1 */
> 	/* sum members: 12, holes: 1, sum holes: 4 */
> 	/* last cacheline: 16 bytes */
> };
> 
> So on 64 bits we have a hole because pointers are aligned at word-size
> boundaries, changing it to 4 bytes:
> 
> [acme@doppio pahole]$ build/pahole -w 4 -C e1000_opt_list \
> /usr/lib/debug/lib/modules/2.6.21-65.el5rt/kernel/drivers/net/e1000/e1000.ko.debug
> struct e1000_opt_list {
> 	int                        i;                    /*     0     4 */
> 
> 	/* XXX 4 bytes hole, try to pack */
> 
> 	char *                     str;                  /*     8     4 */
> 
> 	/* size: 12, cachelines: 1 */
> 	/* sum members: 8, holes: 1, sum holes: 4 */
> 	/* last cacheline: 12 bytes */
> };
> 
> The pointer size was correctly changed to 4 and the size reduced to 12,
> but we should have subtracted 4 bytes from 'str' offset and the hole
> would disappear and the size becomes 8.
> 
> Working on it.

Partially fixed, which says a lot about how bad class__fixup_alignment
is :-\ Only holes after unions are not being fixed up, still scratching
my head on why this is the case.

Anyway:

[acme@doppio pahole]$ build/pahole -w 4 -C e1000_opt_list \
/usr/lib/debug/lib/modules/2.6.21-65.el5rt/kernel/drivers/net/e1000/e1000.ko.debug
struct e1000_opt_list {
	int                        i;                    /*     0     4 */
	char *                     str;                  /*     4     4 */

	/* size: 8, cachelines: 1 */
	/* last cacheline: 8 bytes */
};

- Arnaldo
-
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Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-10 12:42 jamal
2008-01-10 13:39 ` Arnaldo Carvalho de Melo
     [not found]   ` <20080110133926.GF22437-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-10 13:55     ` jamal
2008-01-10 14:06       ` Arnaldo Carvalho de Melo
     [not found]         ` <20080110140635.GG22437-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-10 16:39           ` Arnaldo Carvalho de Melo
     [not found]             ` <20080110163959.GJ22437-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-10 21:37               ` jamal
2008-01-10 21:44                 ` Arnaldo Carvalho de Melo
     [not found]                   ` <20080110214438.GT22437-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-11  0:45                     ` jamal
2008-01-11  1:04                       ` jamal
2008-01-10 21:39               ` Arnaldo Carvalho de Melo
     [not found]                 ` <20080110213909.GS22437-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-10 21:41                   ` jamal
2008-01-12 15:21                     ` Arnaldo Carvalho de Melo
     [not found]                       ` <20080112152109.GA23567-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-12 15:54                         ` Changing the word-size was: " Arnaldo Carvalho de Melo
     [not found]                           ` <20080112155404.GB23567-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-12 16:28                             ` Arnaldo Carvalho de Melo [this message]
     [not found]                               ` <20080112162808.GC23567-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-12 17:28                                 ` Arnaldo Carvalho de Melo
     [not found]                                   ` <20080112172856.GD23567-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-12 18:08                                     ` jamal
2008-01-12 18:42                                       ` Arnaldo Carvalho de Melo
     [not found]                                         ` <20080112184211.GA17675-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-13  0:42                                           ` jamal
2008-01-13  1:15                                             ` jamal
     [not found]                                               ` <20080113163106.GE17675@ghostprotocols.net>
     [not found]                                                 ` <20080113163106.GE17675-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-13 18:07                                                   ` Arnaldo Carvalho de Melo
     [not found]                                                     ` <20080113180730.GG17675-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-13 18:19                                                       ` Arnaldo Carvalho de Melo
     [not found]                                                         ` <20080113181901.GH17675-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-13 18:26                                                           ` Arnaldo Carvalho de Melo
     [not found]                                                             ` <20080113182657.GI17675-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-13 19:13                                                               ` jamal
2008-01-12 21:36                                     ` Arnaldo Carvalho de Melo
     [not found]                                       ` <20080112213635.GC17675-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>
2008-01-12 22:08                                         ` Arnaldo Carvalho de Melo

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