linux-kernel - Re: [PATCH 00/13] convert block layer to bioset_init()/mempool

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Message-ID: <20180522064118.GA18704@infradead.org>
Date:   Mon, 21 May 2018 23:41:18 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Kent Overstreet <kent.overstreet@...il.com>
Cc:     Mike Snitzer <snitzer@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        hch@...radead.org, colyli@...e.de, darrick.wong@...cle.com,
        clm@...com, bacik@...com, linux-xfs@...r.kernel.org,
        drbd-dev@...ts.linbit.com, linux-btrfs@...r.kernel.org,
        linux-raid@...r.kernel.org, neilb@...e.com
Subject: Re: [PATCH 00/13] convert block layer to bioset_init()/mempool_init()

On Mon, May 21, 2018 at 07:38:55PM -0400, Kent Overstreet wrote:
> On Mon, May 21, 2018 at 02:24:32PM -0400, Mike Snitzer wrote:
> > Every single data structure change in this series should be reviewed for
> > unforeseen alignment consequences.  Jens seemed to say that is
> > worthwhile.  Not sure if he'll do it or we divide it up.  If we divide
> > it up a temp topic branch should be published for others to inspect.
> > 
> > Could be alignment hasn't been a historic concern for a bunch of the
> > data structures changed in this series.. if so then all we can do is fix
> > up any obvious potential for false sharing.
> 
> Honestly, I almost never worry about alignment... the very few times I do care,
> I use __cacheline_aligned_in_smp.

And that generally is the right stratgey.  If Mike really doesn't want
a change we can just open code the kmalloc for the bio set there, the
important point is that we should not keep the old API around for no
good reason.