linux-kernel - Re: [PATCH] drm: Reduce object size of DRM_ERROR and DRM

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Date:   Thu, 15 Mar 2018 09:29:54 -0700
From:   Joe Perches <joe@...ches.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm: Reduce object size of DRM_ERROR and DRM_DEBUG uses

On Thu, 2018-03-15 at 18:14 +0200, Ville Syrjälä wrote:
> > There's no trade-off in this patch for faster/larger.
> > This patch is simply smaller.  Smaller is better.
> 
> This feels a bit like saying pink is better than red because it's
> more pink.

Silly.  If you can't say smaller total object code that
performs the same task identically is better, I think
we can't discuss much of anything about code together.

Any printk related mechanism is not fast-path so any
icache dilution isn't an issue.

> That said, I'm not arguing against this patch as such. Making things
> smaller "just because" usually doesn't cause problems.

It seems more like you haven't read the patch.

>  But I was
> hoping that we might be after some more tangible gains here, and
> thus pointed out that there may be a better way to achieve even
> bigger gains.

Sure, it's just any such a discussion should not affect
this patch being applied.

This patch reduces the argument count of the drm_printk
(now drm_dbg) call and so is faster to execute even if
the emit test is internal to the drm_dbg function.