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Message-ID: <49D461F8.20906@cosmosbay.com>
Date: Thu, 02 Apr 2009 08:58:00 +0200
From: Eric Dumazet <dada1@...mosbay.com>
To: "David S. Miller" <davem@...emloft.net>
CC: Linux Netdev List <netdev@...r.kernel.org>
Subject: [PATCH] socket: use percpu_add() while updating sockets_in_use
sock_alloc() currently uses following code to update sockets_in_use
get_cpu_var(sockets_in_use)++;
put_cpu_var(sockets_in_use);
This translates to :
c0436274: b8 01 00 00 00 mov $0x1,%eax
c0436279: e8 42 40 df ff call c022a2c0 <add_preempt_count>
c043627e: bb 20 4f 6a c0 mov $0xc06a4f20,%ebx
c0436283: e8 18 ca f0 ff call c0342ca0 <debug_smp_processor_id>
c0436288: 03 1c 85 60 4a 65 c0 add -0x3f9ab5a0(,%eax,4),%ebx
c043628f: ff 03 incl (%ebx)
c0436291: b8 01 00 00 00 mov $0x1,%eax
c0436296: e8 75 3f df ff call c022a210 <sub_preempt_count>
c043629b: 89 e0 mov %esp,%eax
c043629d: 25 00 e0 ff ff and $0xffffe000,%eax
c04362a2: f6 40 08 08 testb $0x8,0x8(%eax)
c04362a6: 75 07 jne c04362af <sock_alloc+0x7f>
c04362a8: 8d 46 d8 lea -0x28(%esi),%eax
c04362ab: 5b pop %ebx
c04362ac: 5e pop %esi
c04362ad: c9 leave
c04362ae: c3 ret
c04362af: e8 cc 5d 09 00 call c04cc080 <preempt_schedule>
c04362b4: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi
c04362b8: eb ee jmp c04362a8 <sock_alloc+0x78>
While percpu_add(sockets_in_use, 1) translates to a single instruction :
c0436275: 64 83 05 20 5f 6a c0 addl $0x1,%fs:0xc06a5f20
Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
diff --git a/net/socket.c b/net/socket.c
index 91d0c02..791d71a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -493,8 +493,7 @@ static struct socket *sock_alloc(void)
inode->i_uid = current_fsuid();
inode->i_gid = current_fsgid();
- get_cpu_var(sockets_in_use)++;
- put_cpu_var(sockets_in_use);
+ percpu_add(sockets_in_use, 1);
return sock;
}
@@ -536,8 +535,7 @@ void sock_release(struct socket *sock)
if (sock->fasync_list)
printk(KERN_ERR "sock_release: fasync list not empty!\n");
- get_cpu_var(sockets_in_use)--;
- put_cpu_var(sockets_in_use);
+ percpu_sub(sockets_in_use, 1);
if (!sock->file) {
iput(SOCK_INODE(sock));
return;
--
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