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

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Date:   Thu, 15 Mar 2018 15:04:52 +0100
From:   Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Joe Perches <joe@...ches.com>
Cc:     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

Op 15-03-18 om 14:30 schreef Ville Syrjälä:
> On Tue, Mar 13, 2018 at 03:02:15PM -0700, Joe Perches wrote:
>> drm_printk is used for both DRM_ERROR and DRM_DEBUG with unnecessary
>> arguments that can be removed by creating separate functins.
>>
>> Create specific functions for these calls to reduce x86/64 defconfig
>> size by ~20k.
>>
>> Modify the existing macros to use the specific calls.
>>
>> new:
>> $ size -t drivers/gpu/drm/built-in.a | tail -1
>> 1876562	  44542	    995	1922099	 1d5433	(TOTALS)
>>
>> old:
>> $ size -t drivers/gpu/drm/built-in.a | tail -1
>> 1897565	  44542	    995	1943102	 1da63e	(TOTALS)
>>
>> Miscellanea:
>>
>> o intel_display requires a change to use the specific calls.
> How much would we lose if we move the (drm_debug&FOO) outside the
> functions again? I'm somewhat concerned about all the function call
> overhead when debugs aren't even enabled.

Upstream:
   text    data     bss     dec     hex filename
 377143    5689    4352  387184   5e870 drivers/gpu/drm/drm.ko

With this patch:
 373831    5689    4352  383872   5db80 drivers/gpu/drm/drm.ko

Moving the if outside (below):
 377629    5689    4352  387670   5ea56 drivers/gpu/drm/drm.ko

Bye savings..

I don't think there are any places in which the debug output is performance sensitive,
so I'm ok with not inlining.
---
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index 79abf6d5b4db..928822403a59 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -89,14 +89,11 @@ void drm_dev_printk(const struct device *dev, const char *level,
 }
 EXPORT_SYMBOL(drm_dev_printk);
 
-void drm_dbg(unsigned int category, const char *format, ...)
+void __drm_dbg(const char *format, ...)
 {
 	struct va_format vaf;
 	va_list args;
 
-	if (!(drm_debug & category))
-		return;
-
 	va_start(args, format);
 	vaf.fmt = format;
 	vaf.va = &args;
@@ -106,7 +103,7 @@ void drm_dbg(unsigned int category, const char *format, ...)
 
 	va_end(args);
 }
-EXPORT_SYMBOL(drm_dbg);
+EXPORT_SYMBOL(__drm_dbg);
 
 void drm_err(const char *format, ...)
 {
diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index 3a40c5a3a5fa..2a145b97bdfc 100644
--- a/include/drm/drm_print.h
+++ b/include/drm/drm_print.h
@@ -200,8 +200,17 @@ __printf(6, 7)
 void drm_dev_printk(const struct device *dev, const char *level,
 		    unsigned int category, const char *function_name,
 		    const char *prefix, const char *format, ...);
-__printf(2, 3)
-void drm_dbg(unsigned int category, const char *format, ...);
+
+__printf(1, 2)
+void __drm_dbg(const char *format, ...);
+
+
+#define drm_dbg(category, format, ...) \
+	do {	\
+		if (drm_debug & category)	\
+			__drm_dbg(format, ## __VA_ARGS__);	\
+	} while (0)
+
 __printf(1, 2)
 void drm_err(const char *format, ...);