linux-kernel - Re: [RFC PATCH] treewide: remove GFP

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Message-ID: <20170825080442.GF25498@dhcp22.suse.cz>
Date:   Fri, 25 Aug 2017 10:04:42 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Pavel Machek <pavel@....cz>
Cc:     linux-mm@...ck.org, Mel Gorman <mgorman@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Neil Brown <neilb@...e.de>,
        Theodore Ts'o <tytso@....edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] treewide: remove GFP_TEMPORARY allocation flag

On Fri 25-08-17 09:28:19, Pavel Machek wrote:
> On Fri 2017-08-25 08:35:46, Michal Hocko wrote:
> > On Wed 23-08-17 19:57:09, Pavel Machek wrote:
[...]
> > > Dunno. < 1msec probably is temporary, 1 hour probably is not. If it causes
> > > problems, can you just #define GFP_TEMPORARY GFP_KERNEL ? Treewide replace,
> > > and then starting again goes not look attractive to me.
> > 
> > I do not think we want a highlevel GFP_TEMPORARY without any meaning.
> > This just supports spreading the flag usage without a clear semantic
> > and it will lead to even bigger mess. Once we can actually define what
> > the flag means we can also add its users based on that new semantic.
> 
> It has real meaning.

Which is?
 
> You can define more exact meaning, and then adjust the usage. But
> there's no need to do treewide replacement...

I have checked most of them and except for the initially added onces the
large portion where added without a good reasons or even break an
intuitive meaning by taking locks.

Seriously, if we need a short term semantic it should be clearly defined
first.

Is there any specific case why you think this patch is in a wrong
direction? E.g. a measurable regression?

-- 
Michal Hocko
SUSE Labs