From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Denis Efremov <efremov@linux.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Michal Marek <michal.lkml@markovi.net>,
Emil Velikov <emil.l.velikov@gmail.com>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions
Date: Wed, 31 Jul 2019 02:21:46 +0900 [thread overview]
Message-ID: <CAK7LNAS8fkV5b+Sk+_W_C97xe3GCK-JysYSGuhB9t35yoAuCzg@mail.gmail.com> (raw)
In-Reply-To: <d26ff0d1-fc45-d5b5-fe84-26fa9df09c3e@linux.com>
On Wed, Jul 31, 2019 at 1:44 AM Denis Efremov <efremov@linux.com> wrote:
>
> On 30.07.2019 19:29, Masahiro Yamada wrote:
> > I prefer this, but why do you need to check type?
> >
> > Doesn't this work?
> >
> > for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
> > unsigned char bind = ELF_ST_BIND(sym->st_info);
> >
> > struct symbol *s = find_symbol(remove_dot(info.strtab +
> > sym->st_name));
> >
> > if (s && (bind == STB_GLOBAL || bind == STB_WEAK))
> > s->is_static = 0;
> > }
>
> This works. However, I thought it will be too costly to call find_symbol
> on each symbol. Hence, 'type == STT_OBJECT || type == STT_FUNC || type
> == STT_NOTYPE' is a small performance optimization because we need to
> check only variables and functions. Is it worth to remove it in v4?
>
> Denis
I checked the symbol table for ppc64_defconfig.
The following is the number of entries
for each combination of type and bind.
[1] type: STT_NOTYPE, bind: STB_LOCAL -> 39502 entries
[2] type: STT_NOTYPE, bind: STB_GLOBAL -> 30161 entries
[3] type: STT_NOTYPE, bind: STB_WEAK -> 5 entries
[4] type: STT_OBJECT, bind: STB_LOCAL -> 60326 entries
[5] type: STT_OBJECT, bind: STB_GLOBAL -> 4126 entries
[6] type: STT_OBJECT, bind: STB_WEAK -> 11 entries
[7] type: STT_FUNC, bind: STB_LOCAL -> 38816 entries
[8] type: STT_FUNC, bind: STB_GLOBAL -> 56196 entries
[9] type: STT_FUNC, bind: STB_WEAK -> 350 entries
[10] type: STT_SECTION, bind: STB_LOCAL -> 9027 entries
[11] type: STT_FILE, bind: STB_LOCAL -> 2918 entries
Checking 'type' beforehand
saves only 11945 look-ups ( [10] + [11]).
You can check 'bind' before the look-up, not after.
If bind == STB_LOCAL, you do not need to lookup the hash-table,
since you do not do anything.
This saves [1], [4], [7], [10], [11].
I think the following is simpler, and works more efficiently.
for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
unsigned char bind = ELF_ST_BIND(sym->st_info);
if (bind == STB_GLOBAL || bind == STB_WEAK) {
struct symbol *s =
find_symbol(remove_dot(info.strtab +
sym->st_name));
if (s)
s->is_static = 0;
}
}
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2019-07-30 17:22 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-14 15:28 [RFC PATCH] modpost: check for static EXPORT_SYMBOL* functions Denis Efremov
2019-07-15 14:43 ` Emil Velikov
2019-07-27 12:55 ` Masahiro Yamada
2019-07-27 19:13 ` Denis Efremov
2019-07-28 2:00 ` Masahiro Yamada
2019-07-28 10:09 ` [PATCH] " Denis Efremov
2019-07-29 3:29 ` Masahiro Yamada
2019-07-29 9:51 ` Denis Efremov
2019-07-29 5:13 ` Stephen Rothwell
2019-07-29 9:16 ` Denis Efremov
2019-07-29 9:32 ` Masahiro Yamada
2019-07-29 12:40 ` Stephen Rothwell
2019-07-29 12:52 ` Denis Efremov
2019-07-29 13:07 ` Stephen Rothwell
2019-07-29 9:22 ` [PATCH v2] " Denis Efremov
2019-07-29 12:20 ` Stephen Rothwell
2019-07-29 12:47 ` Denis Efremov
2019-07-29 14:18 ` [PATCH v3] " Denis Efremov
2019-07-29 22:26 ` Stephen Rothwell
2019-07-30 6:59 ` Denis Efremov
2019-07-30 16:29 ` Masahiro Yamada
2019-07-30 16:44 ` Denis Efremov
2019-07-30 17:21 ` Masahiro Yamada [this message]
2019-07-30 18:11 ` [PATCH v4] " Denis Efremov
2019-07-30 18:15 ` Denis Efremov
2019-07-31 8:54 ` Masahiro Yamada
2019-08-01 2:20 ` Masahiro Yamada
2019-08-01 6:17 ` Denis Efremov
2019-08-01 6:06 ` [PATCH v5] " Denis Efremov
2019-08-07 15:12 ` Masahiro Yamada
2019-08-13 16:07 ` Masahiro Yamada
2019-08-13 21:11 ` Denis Efremov
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