linux-kernel - Re: [PATCH] seq_file: delete small-value optimization

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Message-ID: <20170517103341.GB28488@avx2>
Date:   Wed, 17 May 2017 13:33:41 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     joe@...ches.com
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] seq_file: delete small-value optimization

> Joe Perches wrote:
> 
> On Tue, 2017-05-16 at 23:42 +0300, Alexey Dobriyan wrote:
> > num_to_str() optimizes printing small integers [0..9], so the same
> > check higher in callchain is unnecessary.
> 
> Doesn't the optimization exists for the frequent use of 0
> in seq output?  
> 
> These seq_put_decimal calls are now slightly more expensive.

That additional CALL instruction is hardly measurable so you're adding
branch to skip branch in the next function.