From: Jeff Law <law@redhat.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>,
Peter Zijlstra <peterz@infradead.org>,
gcc-help@gcc.gnu.org
Cc: mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
linux-kernel@vger.kernel.org
Subject: Re: [Q] ld: Does LTO reorder ro variables in two files?
Date: Thu, 19 Dec 2019 08:21:58 -0700 [thread overview]
Message-ID: <db7acdee9a85ce5b74332b3869efa6c9e18bad9e.camel@redhat.com> (raw)
In-Reply-To: <3db1b1c8-0228-56e4-a04f-e8d24cd1dd51@virtuozzo.com>
On Thu, 2019-12-19 at 17:04 +0300, Kirill Tkhai wrote:
> CC: gcc-help@gcc.gnu.org
>
> Hi, gcc guys,
>
> this thread starts here: https://lkml.org/lkml/2019/12/19/403
>
> There are two const variables:
>
> struct sched_class idle_sched_class
> and
> struct sched_class fair_sched_class,
>
> which are declared in two files idle.c and fair.c.
>
> 1)In Makefile the order is: idle.o fair.o
> 2)the variables go to the same ro section
> 3)there is no SORT(.*) keyword in linker script.
>
> Is it always true, that after linkage &idle_sched_class < &fair_sched_class?
I certainly wouldn't depend on it. The first and most obvious problem
is symbol sorting by the linker. Longer term I'd be worried about LTO
reordering things.
In the end I'm pretty sure it'd be well outside what I'd be comfortable
depending on.
jeff
>
next prev parent reply other threads:[~2019-12-19 15:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-19 12:39 [PATCH RFC] sched: Micro optimization in pick_next_task() and in check_preempt_curr() Kirill Tkhai
2019-12-19 13:12 ` Peter Zijlstra
2019-12-19 14:02 ` Peter Zijlstra
2019-12-19 14:25 ` Kirill Tkhai
2019-12-19 14:31 ` Kirill Tkhai
2019-12-19 14:43 ` Steven Rostedt
2019-12-19 14:46 ` Kirill Tkhai
2019-12-19 14:59 ` Steven Rostedt
2019-12-19 15:20 ` [PATCH v2] " Kirill Tkhai
2019-12-19 15:40 ` Steven Rostedt
2019-12-19 16:08 ` Kirill Tkhai
2019-12-19 16:22 ` Steven Rostedt
2019-12-19 20:16 ` Kirill Tkhai
2019-12-19 20:20 ` Steven Rostedt
2019-12-19 16:05 ` Steven Rostedt
2019-12-19 14:04 ` [Q] ld: Does LTO reorder ro variables in two files? Kirill Tkhai
2019-12-19 15:21 ` Jeff Law [this message]
2019-12-19 15:30 ` Kirill Tkhai
2019-12-19 15:45 ` Alexander Monakov
2019-12-19 16:08 ` Kirill Tkhai
2019-12-19 13:50 ` [PATCH RFC] sched: Micro optimization in pick_next_task() and in check_preempt_curr() Steven Rostedt
2019-12-19 13:53 ` Kirill Tkhai
2019-12-19 13:53 ` Peter Zijlstra
2020-06-25 11:53 ` [tip: sched/core] sched: Force the address order of each sched class descriptor tip-bot2 for Steven Rostedt (VMware)
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