linux-kernel - RE: amusing SLUB compaction bug when CC_OPTIMIZE_FOR

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Message-ID: <06329f-e498-ccc-6223-32f87716436d@google.com>
Date:   Fri, 30 Sep 2022 09:21:44 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     David Laight <David.Laight@...lab.com>
cc:     Hugh Dickins <hughd@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        Joel Fernandes <joel@...lfernandes.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: RE: amusing SLUB compaction bug when CC_OPTIMIZE_FOR_SIZE

On Fri, 30 Sep 2022, David Laight wrote:
> > > > Regarding "conflicting" alignment requests: yes, I agree with you,
> > > > it would have to be a toolchain bug if when asked to align 2 and to
> > > > align 4, it chose not to align 4.
> 
> See https://godbolt.org/z/3nGsTaf5e
> the align() directive takes precedence.
> 
> Here you only want to ensure the alignment is at least 4.

Sorry, I don't understand the point you are making,
nor how to deduce it from the link which you give:
I'll leave it to those who understand better.

Hugh