linux-kernel - [PATCH 2/2] UML

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Message-ID: <20070330145257.GA5471@c2.user-mode-linux.org>
Date:	Fri, 30 Mar 2007 10:52:57 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: [PATCH 2/2] UML - Speed up exec

flush_thread doesn't need to do a full page table walk in order to
clear the address space.  It knows what the end result needs to be, so
it can call unmap directly.

This results in a 10-20% speedup in an exec from bash.

Signed-off-by: Jeff Dike <jdike@...ux.intel.com>
--
 arch/um/kernel/skas/exec.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux-2.6.21-mm/arch/um/kernel/skas/exec.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/kernel/skas/exec.c	2007-03-30 10:28:24.000000000 -0400
+++ linux-2.6.21-mm/arch/um/kernel/skas/exec.c	2007-03-30 10:30:15.000000000 -0400
@@ -17,7 +17,17 @@
 
 void flush_thread_skas(void)
 {
-	force_flush_all();
+	void *data = NULL;
+	unsigned long end = proc_mm ? task_size : CONFIG_STUB_START;
+	int ret;
+
+	ret = unmap(&current->mm->context.skas.id, 0, end, 1, &data);
+	if(ret){
+		printk("flush_thread_skas - clearing address space failed, "
+		       "err = %d\n", ret);
+		force_sig(SIGKILL, current);
+	}
+
 	switch_mm_skas(&current->mm->context.skas.id);
 }
 
-
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