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Message-ID: <bd3806ccc911989c7ef1fed9e8d26a4a5ad347a9.camel@perches.com>
Subject: Re: [PATCH] xfs: Remove noinline from #define STATIC
From:   Joe Perches <joe@perches.com>
To:     Dave Chinner <david@fromorbit.com>,
        Eric Sandeen <sandeen@sandeen.net>
Cc:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Christoph Hellwig <hch@lst.de>, linux-xfs@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
Date:   Mon, 12 Nov 2018 14:30:01 -0800
In-Reply-To: <20181112214515.GN19305@dastard>
References: <7302f4a13c1cbf62b07f636878ce25fcca84b6c4.camel@perches.com>
         <6420cf91-89c8-a876-7a0d-25ab8ba428b8@sandeen.net>
         <20181112214515.GN19305@dastard>
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On Tue, 2018-11-13 at 08:45 +1100, Dave Chinner wrote:
> On Mon, Nov 12, 2018 at 02:12:08PM -0600, Eric Sandeen wrote:
> > On 11/10/18 7:21 PM, Joe Perches wrote:
> > > Reduce total object size quite a bit (~32KB) and presumably
> > > improve performance at the same time.
> > > 
> > > Total object size old vs new (x86-64 defconfig with xfs)
> > > 
> > >     text	   data	    bss	    dec	    hex	filename
> > > - 959351	 165573	    632	1125556	 112cb4	(TOTALS) (old)
> > > + 924683	 165669	    632	1090984	 10a5a8	(TOTALS) (new)
> > 
> > And what does it do to maximum stack excursions?
> 
> Better yet: what does it do to corruption stack traces and debugging
> tools like profiling traces?
> 
> i.e. this noinline directive isn't about stack usage, this is about
> being able to debug production code. Basically the compiler inliner
> is so agressive on static functions that it makes it impossible to
> decipher the stack traces. It flattens them way too much to
> be able to tell how we got to a specific location in the code.
> 
> In reality, being able to find problems quickly and efficiently is
> far more important to us than being able to run everything at
> ludicrous speed....

Is that really a compelling argument given thw ~50:50
split of static/STATIC uses in xfs?

$ git grep -w STATIC fs/xfs/ | wc -l
1064
$ git grep -w static fs/xfs/ | wc -l
942