From: Muli Ben-Yehuda <mulix@mulix.org>
To: Andrew Morton <akpm@osdl.org>
Cc: Jamie Lokier <jamie@shareable.org>,
Linux-Kernel <linux-kernel@vger.kernel.org>
Subject: [PATCH] document optimizing macro for translating PROT_ to VM_ bits
Date: Mon, 29 Sep 2003 12:06:30 +0300 [thread overview]
Message-ID: <20030929090629.GF29313@actcom.co.il> (raw)
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In continuation to the thread at
http://marc.theaimsgroup.com/?l=linux-kernel&m=3D106270456516176&w=2 wrt
translating PROT_(censored) bits to VM_(censored) bits, here's a small
comment only patch to document the optimizing macro Jamie's patch
used. Against 2.6.0-t6, but should apply to anything
recent. Compiles.
Cheers,
Muli
--- linux-2.5/include/linux/mman.h Sun Sep 7 10:05:18 2003
+++ optimizing-macro-2.6.0-t6/include/linux/mman.h Mon Sep 29 11:53:12 2003
@@ -28,7 +28,10 @@
vm_acct_memory(-pages);
}
-/* Optimisation macro. */
+/* Optimisation macro, used to be defined as: */
+/* ((bit1 == bit2) ? (x & bit1) : (x & bit1) ? bit2 : 0) */
+/* but this version is faster */
+/* "check if bit1 is on in 'x'. If it is, return bit2" */
#define _calc_vm_trans(x,bit1,bit2) \
((bit1) <= (bit2) ? ((x) & (bit1)) * ((bit2) / (bit1)) \
: ((x) & (bit1)) / ((bit1) / (bit2)))
--
Muli Ben-Yehuda
http://www.mulix.org
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next reply other threads:[~2003-09-29 9:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-29 9:06 Muli Ben-Yehuda [this message]
2003-09-29 15:34 ` [PATCH] document optimizing macro for translating PROT_ to VM_ bits Jamie Lokier
2003-09-29 15:51 ` Valdis.Kletnieks
2003-09-29 17:11 ` Jamie Lokier
2003-09-29 17:25 ` Maciej Zenczykowski
2003-09-30 2:15 ` Miles Bader
2003-09-30 7:10 ` Muli Ben-Yehuda
2003-09-30 7:34 ` Miles Bader
2003-09-30 7:41 ` Muli Ben-Yehuda
2003-09-30 7:59 ` Miles Bader
2003-09-30 9:24 ` Muli Ben-Yehuda
2003-09-30 10:00 ` Miles Bader
2003-09-30 10:06 ` Miles Bader
2003-10-02 11:37 ` Muli Ben-Yehuda
2003-09-30 10:35 ` Thomas Schlichter
2003-09-30 8:02 ` Frédéric St-Martin
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