linux-kernel - Re: [PATCH v2] blkdev: Replace blksize

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Date:   Tue, 2 Jun 2020 08:13:05 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Tao pilgrim <pilgrimtao@...il.com>, Jens Axboe <axboe@...nel.dk>,
        sth@...ux.ibm.com, viro@...iv.linux.org.uk, clm@...com,
        jaegeuk@...nel.org, hch@...radead.org,
        Mark Fasheh <mark@...heh.com>, dhowells@...hat.com,
        balbi@...nel.org, damien.lemoal@....com, bvanassche@....org,
        ming.lei@...hat.com, martin.petersen@...cle.com, satyat@...gle.com,
        chaitanya.kulkarni@....com, houtao1@...wei.com,
        asml.silence@...il.com, ajay.joshi@....com,
        linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>, hoeppner@...ux.ibm.com,
        heiko.carstens@...ibm.com, gor@...ux.ibm.com,
        borntraeger@...ibm.com, linux-s390@...r.kernel.org,
        sagi@...mberg.me, linux-nvme@...ts.infradead.org,
        linux-usb@...r.kernel.org, Josef Bacik <josef@...icpanda.com>,
        dsterba@...e.com, linux-btrfs@...r.kernel.org, chao@...nel.org,
        linux-f2fs-devel@...ts.sourceforge.net, darrick.wong@...cle.com,
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        jlbec@...lplan.org, joseph.qi@...ux.alibaba.com,
        ocfs2-devel@....oracle.com, deepa.kernel@...il.com
Subject: Re: [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

On Tue, Jun 02, 2020 at 07:51:52AM +0200, Christoph Hellwig wrote:
> On Mon, Jun 01, 2020 at 10:44:26AM +0200, Greg KH wrote:
> > But does this code path actually show up anywhere that is actually
> > measurable as mattering?
> > 
> > If so, please show that benchmark results.
> 
> I think the requests are starting to be a bit unreasonable.  Tao is
> replacing a reimplementation of a standard function with that standard
> function / compiler builtin.  We don't put such a high burden on that.

That's fine, but to say it is "faster" usually means we want to see it
actually going faster somehow :)

> And once the proper existing fields are used where possible as shown
> in my reply just replacing the rest seems totally obvious - quite
> contrary I think keeping a reimplementation would need a high bar.

Your patch makes sense, I was not objecting to that.

thanks,

greg k-h