From: Denis Vlasenko <vda@ilport.com.ua>
To: Arjan van de Ven <arjan@infradead.org>, linux-os@analogic.com
Cc: Jesper Juhl <juhl-lkml@dif.dk>,
ext2-devel@lists.sourceforge.net,
Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
Date: Sun, 27 Mar 2005 15:51:18 +0300 [thread overview]
Message-ID: <200503271551.18342.vda@ilport.com.ua> (raw)
In-Reply-To: <1111913130.6297.24.camel@laptopd505.fenrus.org>
> > It's impossible to be otherwise. A call requires
> > that the return address be written to memory (the stack),
> > using register indirection (the stack-pointer).
>
> and it's a so common pattern that it's optimized to death. Internally a
> call gets transformed to 2 uops or so, one is push eip, the other is the
> jmp (which gets then just absorbed by the "what is the next eip" logic,
> just as a "jmp"s are 0 cycles)
Arjan, you overlook the fact that kfree() contains 'if(!p) return;' too.
call + test-and-branch can never be faster than test+and+branch.
Maybe on the really clever CPU it can take the same time, but not faster...
--
vda
next prev parent reply other threads:[~2005-03-27 12:51 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-25 22:08 [PATCH] no need to check for NULL before calling kfree() - fs/ext2/ Jesper Juhl
2005-03-25 22:29 ` linux-os
2005-03-25 22:44 ` Jesper Juhl
2005-03-26 7:50 ` Pekka Enberg
2005-03-26 8:32 ` Arjan van de Ven
2005-03-26 23:21 ` [PATCH] no need to check for NULL before calling kfree() -fs/ext2/ linux-os
2005-03-26 23:34 ` Marcin Dalecki
2005-03-27 2:00 ` Horst von Brand
2005-03-27 3:18 ` Marcin Dalecki
2005-03-27 22:12 ` linux-os
2005-03-26 23:54 ` Jesper Juhl
2005-03-27 0:05 ` Lee Revell
2005-03-27 10:55 ` Jesper Juhl
2005-03-27 14:56 ` Paul Jackson
2005-03-27 15:12 ` Jan Engelhardt
2005-03-27 17:40 ` Dave Jones
2005-03-27 18:17 ` Jan Engelhardt
2005-03-27 19:25 ` Pekka Enberg
2005-03-27 22:56 ` Jesper Juhl
2005-03-28 4:53 ` Paul Jackson
2005-03-30 18:57 ` Jesper Juhl
2005-03-28 1:20 ` Horst von Brand
2005-03-28 4:10 ` Paul Jackson
2005-03-28 12:58 ` Geert Uytterhoeven
2005-03-29 2:52 ` Lee Revell
2005-03-29 6:30 ` Pekka Enberg
2005-03-29 7:06 ` Jan Engelhardt
2005-03-29 7:24 ` Pekka J Enberg
2005-03-30 2:44 ` Paul Jackson
2005-03-30 6:13 ` Pekka J Enberg
2005-03-30 6:16 ` Paul Jackson
2005-03-30 7:15 ` P Lavin
2005-03-30 14:20 ` Jesper Juhl
2005-03-30 19:10 ` Jesper Juhl
2005-04-09 2:21 ` Jesper Juhl
2005-03-28 4:07 ` [PATCH] " Paul Jackson
2005-03-27 8:45 ` Arjan van de Ven
2005-03-27 12:51 ` Denis Vlasenko [this message]
2005-03-27 14:28 ` Arjan van de Ven
2005-03-27 23:13 ` [PATCH] no need to check for NULL before calling kfree()-fs/ext2/ linux-os
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