linux-kernel - Re: [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)

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Message-ID: <20190930080613.GA5379@lst.de>
Date:   Mon, 30 Sep 2019 10:06:13 +0200
From:   Christoph Hellwig <hch@....de>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Ming Lei <ming.lei@...hat.com>,
        Dave Chinner <david@...morbit.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@....de>, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        linux-btrfs@...r.kernel.org, Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for
 kmalloc(power-of-two)

On Mon, Sep 23, 2019 at 06:36:32PM +0200, Vlastimil Babka wrote:
> So if anyone thinks this is a good idea, please express it (preferably
> in a formal way such as Acked-by), otherwise it seems the patch will be
> dropped (due to a private NACK, apparently).

I think we absolutely need something like this, and I'm sick and tired
of the people just claiming there is no problem.

>From the user POV I don't care if aligned allocations need a new
GFP_ALIGNED flag or not, but as far as I can tell the latter will
probably cause more overhead in practice than not having it.

So unless someone comes up with a better counter proposal to provide
aligned kmalloc of some form that doesn't require a giant amount of
boilerplate code in the users:

Acked^2-by: Christoph Hellwig <hch@....de>