linux-kernel - Re: [PATCH] mm/debug: sync up latest migrate_reason to migrate_reason

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Date:   Mon, 20 Sep 2021 17:14:48 +0800
From:   Weizhao Ouyang <o451686892@...il.com>
To:     John Hubbard <jhubbard@...dia.com>,
        "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Oscar Salvador <osalvador@...e.de>,
        Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/debug: sync up latest migrate_reason to
 migrate_reason_names


On 2021/9/19 13:38, John Hubbard wrote:
> On 9/18/21 00:03, Weizhao Ouyang wrote:
> ...
>>   Anyway, I didn't find a simply way the build the "everywhere" relationship behind
>> the packaged TRACE_DEFINE_ENUM , what do you think.
>>
> It's actually pretty easy, unless I'm unknowingly violating some rule
> here. But I did review tracing a bit before diving in, and I think this
> is reasonable.
>
> The trace macros EM(), EMe(), and MIGRATE_REASON are flexible enough to
> get whatever you want, out of them. So, the trace header can be the one
> location for the definition of the enum-to-string mapping.
>
> The key is to move the enum to a common header file that both the trace
> system (trace/events/migrate.h) and the migrate header
> (include/linux/migrate.h) can include. Fortunately, that's already been
> started for enum migrate_mode: there is migrate_mode.h.
>
> So it all works approximately like this, below. (I'll attach a
> white-space-correct diff that you can apply directly, too). I've
> compiled tested and rebooted with it, but haven't checked much more
> than that yet.

Thanks for your detailed patch! Yeah, if we move the enum migrate_reason to
another header file it will attach it easily. The previous mail I said the
tricky point is that we build the "everywhere relationship" on the basis of
maintaining the original file structure, sorry for the confusing misleading.
I think we should not change a lot for a slight synchronization.

For now we can just apply the update in migrate_reason_name(maybe leave a
comment to notify) on this patch, I will send v2 patch soon include the "cma"
update. As for the trace_event synchronization, we can figure out a more
generic implementation in the future, so that other subsystem can use it to
catch a string info from its trace event header.

Thanks,
Weizhao