linux-kernel - [PATCH 7/7] Remove expensive WARN_ON in pagefault_disabled

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Message-Id: <20170315021431.13107-8-andi@firstfloor.org>
Date:   Tue, 14 Mar 2017 19:14:31 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 7/7] Remove expensive WARN_ON in pagefault_disabled_dec

From: Andi Kleen <ak@...ux.intel.com>

pagefault_disabled_dec is frequently used inline, and it has a WARN_ON
for underflow that expands to about 6.5k of extra code. The warning
doesn't seem to be that useful and worth so much code so remove it.

If it was needed could make it depending on some debug kernel option.

Saves ~6.5k in my kernel

   text    data     bss     dec     hex filename
9039417 5367568 11116544        25523529        1857549 vmlinux-before-pf
9032805 5367568 11116544        25516917        1855b75 vmlinux-pf

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 include/linux/uaccess.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index f30c187ed785..b691aad918fb 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -12,7 +12,6 @@ static __always_inline void pagefault_disabled_inc(void)
 static __always_inline void pagefault_disabled_dec(void)
 {
 	current->pagefault_disabled--;
-	WARN_ON(current->pagefault_disabled < 0);
 }
 
 /*
-- 
2.9.3