1021.lowlatency.patch

sm86xx内核源包括补丁（ GPL ）的

diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/arch/i386/config.in linuxmips-2.4.30/arch/i386/config.in
--- linuxmips-2.4.30.ref/arch/i386/config.in	2005-07-21 19:15:29.000000000 -0700
+++ linuxmips-2.4.30/arch/i386/config.in	2005-07-22 09:36:02.000000000 -0700
@@ -25,6 +25,9 @@
 
 mainmenu_option next_comment
 comment 'Processor type and features'
+bool 'Low latency scheduling' CONFIG_LOLAT
+dep_bool 'Control low latency with sysctl' CONFIG_LOLAT_SYSCTL $CONFIG_LOLAT
+
 choice 'Processor family' \
 	"386					CONFIG_M386 \
 	 486					CONFIG_M486 \
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/arch/mips/config-shared.in linuxmips-2.4.30/arch/mips/config-shared.in
--- linuxmips-2.4.30.ref/arch/mips/config-shared.in	2005-07-21 19:15:30.000000000 -0700
+++ linuxmips-2.4.30/arch/mips/config-shared.in	2005-07-22 09:40:58.000000000 -0700
@@ -802,6 +802,9 @@
 
 bool 'Networking support' CONFIG_NET
 
+bool 'Low latency scheduling' CONFIG_LOLAT
+dep_bool '  Control low latency with sysctl' CONFIG_LOLAT_SYSCTL $CONFIG_LOLAT
+
 if [ "$CONFIG_ACER_PICA_61" = "y" -o \
      "$CONFIG_CASIO_E55" = "y" -o \
      "$CONFIG_DECSTATION" = "y" -o \
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/Documentation/Configure.help linuxmips-2.4.30/Documentation/Configure.help
--- linuxmips-2.4.30.ref/Documentation/Configure.help	2005-07-21 19:15:31.000000000 -0700
+++ linuxmips-2.4.30/Documentation/Configure.help	2005-07-22 09:36:03.000000000 -0700
@@ -109,6 +109,23 @@
 
   Unless you know what you are doing you *should not* enable this option.
 
+Low latency scheduling
+CONFIG_LOLAT
+  This enables low latency scheduling, with reduces the scheduling
+  latency of the kernel.  This makes the kernel more responsive, and
+  potentially increases its bandwidth; since threads waste less time
+  waiting for execution.
+
+  If you don't know what to do here, say Y.
+
+Control low latency with sysctl
+CONFIG_LOLAT_SYSCTL
+  If you say Y here, you will be able to control low latency
+  scheduling using /proc/sys/kernel/lowlatency.  It will default
+  to '0': low latency disabled.
+
+  If you say N here, then low latency scheduling is always enabled.
+
 Symmetric Multi-Processing support
 CONFIG_SMP
   This enables support for systems with more than one CPU. If you have
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/block/ll_rw_blk.c linuxmips-2.4.30/drivers/block/ll_rw_blk.c
--- linuxmips-2.4.30.ref/drivers/block/ll_rw_blk.c	2004-11-18 16:28:36.000000000 -0800
+++ linuxmips-2.4.30/drivers/block/ll_rw_blk.c	2005-07-22 09:36:02.000000000 -0700
@@ -1328,6 +1328,7 @@
 			kstat.pgpgin += count;
 			break;
 	}
+	conditional_schedule();
 }
 
 /**
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/char/mem.c linuxmips-2.4.30/drivers/char/mem.c
--- linuxmips-2.4.30.ref/drivers/char/mem.c	2004-08-14 11:38:49.000000000 -0700
+++ linuxmips-2.4.30/drivers/char/mem.c	2005-07-22 09:36:02.000000000 -0700
@@ -401,7 +401,7 @@
 		if (count > size)
 			count = size;
 
-		zap_page_range(mm, addr, count);
+		zap_page_range(mm, addr, count, 0);
         	zeromap_page_range(addr, count, PAGE_COPY);
 
 		size -= count;
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/char/random.c linuxmips-2.4.30/drivers/char/random.c
--- linuxmips-2.4.30.ref/drivers/char/random.c	2005-01-13 02:59:03.000000000 -0800
+++ linuxmips-2.4.30/drivers/char/random.c	2005-07-22 09:36:02.000000000 -0700
@@ -1378,6 +1378,11 @@
 		buf += i;
 		ret += i;
 		add_timer_randomness(&extract_timer_state, nbytes);
+#if LOWLATENCY_NEEDED
+		/* This can happen in softirq's, but that's what we want */
+		if (conditional_schedule_needed())
+			break;
+#endif
 	}
 
 	/* Wipe data just returned from memory */
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/i2c/i2c-algo-bit.c linuxmips-2.4.30/drivers/i2c/i2c-algo-bit.c
--- linuxmips-2.4.30.ref/drivers/i2c/i2c-algo-bit.c	2005-03-18 04:13:25.000000000 -0800
+++ linuxmips-2.4.30/drivers/i2c/i2c-algo-bit.c	2005-07-22 09:36:03.000000000 -0700
@@ -367,6 +367,7 @@
 			return (retval<0)? retval : -EFAULT;
 			        /* got a better one ?? */
 		}
+		conditional_schedule();
 #if 0
 		/* from asm/delay.h */
 		__delay(adap->mdelay * (loops_per_sec / 1000) );
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/i2c/i2c-core.c linuxmips-2.4.30/drivers/i2c/i2c-core.c
--- linuxmips-2.4.30.ref/drivers/i2c/i2c-core.c	2004-11-29 09:47:16.000000000 -0800
+++ linuxmips-2.4.30/drivers/i2c/i2c-core.c	2005-07-22 09:36:02.000000000 -0700
@@ -724,6 +724,8 @@
 {
 	int ret;
 
+	conditional_schedule();
+
 	if (adap->algo->master_xfer) {
  	 	DEB2(printk(KERN_DEBUG "i2c-core.o: master_xfer: %s with %d msgs.\n",
 		            adap->name,num));
@@ -746,6 +748,8 @@
 	struct i2c_adapter *adap=client->adapter;
 	struct i2c_msg msg;
 
+	conditional_schedule();
+
 	if (client->adapter->algo->master_xfer) {
 		msg.addr   = client->addr;
 		msg.flags = client->flags & I2C_M_TEN;
@@ -775,6 +779,9 @@
 	struct i2c_adapter *adap=client->adapter;
 	struct i2c_msg msg;
 	int ret;
+
+	conditional_schedule();
+
 	if (client->adapter->algo->master_xfer) {
 		msg.addr   = client->addr;
 		msg.flags = client->flags & I2C_M_TEN;
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/video/fbcon-cfb16.c linuxmips-2.4.30/drivers/video/fbcon-cfb16.c
--- linuxmips-2.4.30.ref/drivers/video/fbcon-cfb16.c	2001-11-05 16:55:18.000000000 -0800
+++ linuxmips-2.4.30/drivers/video/fbcon-cfb16.c	2005-07-22 09:36:03.000000000 -0700
@@ -15,6 +15,7 @@
 #include <linux/string.h>
 #include <linux/fb.h>
 #include <asm/io.h>
+#include <linux/sched.h>
 
 #include <video/fbcon.h>
 #include <video/fbcon-cfb16.h>
@@ -189,6 +190,7 @@
     case 4:
     case 8:
 	while (count--) {
+	    conditional_schedule();
 	    c = scr_readw(s++) & p->charmask;
 	    cdat = p->fontdata + c * fontheight(p);
 	    for (rows = fontheight(p), dest = dest0; rows--; dest += bytes) {
@@ -206,6 +208,7 @@
     case 12:
     case 16:
 	while (count--) {
+	    conditional_schedule();
 	    c = scr_readw(s++) & p->charmask;
 	    cdat = p->fontdata + (c * fontheight(p) << 1);
 	    for (rows = fontheight(p), dest = dest0; rows--; dest += bytes) {
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/fs/buffer.c linuxmips-2.4.30/fs/buffer.c
--- linuxmips-2.4.30.ref/fs/buffer.c	2004-11-18 16:28:47.000000000 -0800
+++ linuxmips-2.4.30/fs/buffer.c	2005-07-22 09:36:02.000000000 -0700
@@ -261,8 +261,10 @@
 
 		if (dev != NODEV && bh->b_dev != dev)
 			continue;
-		if (test_and_set_bit(BH_Lock, &bh->b_state))
+		if (test_and_set_bit(BH_Lock, &bh->b_state)) {
+			__refile_buffer(bh);
 			continue;
+		}
 		if (buffer_delay(bh)) {
 			if (write_buffer_delay(bh)) {
 				if (count)
@@ -278,6 +280,7 @@
 
 			spin_unlock(&lru_list_lock);
 			write_locked_buffers(array, count);
+			conditional_schedule();
 			return -EAGAIN;
 		}
 		unlock_buffer(bh);
@@ -311,12 +314,19 @@
 	struct buffer_head * next;
 	int nr;
 
-	next = lru_list[index];
 	nr = nr_buffers_type[index];
+repeat:
+	next = lru_list[index];
 	while (next && --nr >= 0) {
 		struct buffer_head *bh = next;
 		next = bh->b_next_free;
 
+		if (conditional_schedule_needed()) {
+			spin_unlock(&lru_list_lock);
+			unconditional_schedule();
+			spin_lock(&lru_list_lock);
+			goto repeat;
+		}
 		if (!buffer_locked(bh)) {
 			if (refile)
 				__refile_buffer(bh);
@@ -324,7 +334,6 @@
 		}
 		if (dev != NODEV && bh->b_dev != dev)
 			continue;
-
 		get_bh(bh);
 		spin_unlock(&lru_list_lock);
 		wait_on_buffer (bh);
@@ -357,6 +366,15 @@
 {
 	int err = 0;
 
+#if LOWLATENCY_NEEDED
+	/*
+	 * syncing devA when there are lots of buffers dirty against
+	 * devB is expensive.
+	 */
+	if (enable_lowlatency)
+		dev = NODEV;
+#endif
+
 	/* One pass for no-wait, three for wait:
 	 * 0) write out all dirty, unlocked buffers;
 	 * 1) wait for all dirty locked buffers;
@@ -724,6 +742,7 @@
 	int i, nlist, slept;
 	struct buffer_head * bh, * bh_next;
 	kdev_t dev = to_kdev_t(bdev->bd_dev);	/* will become bdev */
+	int lolat_retry = 0;
 
  retry:
 	slept = 0;
@@ -741,6 +760,17 @@
 			/* Not hashed? */
 			if (!bh->b_pprev)
 				continue;
+
+			if (lolat_retry < 10 && conditional_schedule_needed()) {
+				get_bh(bh);
+				spin_unlock(&lru_list_lock);
+				unconditional_schedule();
+				spin_lock(&lru_list_lock);
+				put_bh(bh);
+				slept = 1;
+				lolat_retry++;
+			}
+
 			if (buffer_locked(bh)) {
 				get_bh(bh);
 				spin_unlock(&lru_list_lock);
@@ -892,12 +922,18 @@
 	struct buffer_head *bh;
 	struct list_head tmp;
 	int err = 0, err2;
-	
+	DEFINE_RESCHED_COUNT;
+
 	INIT_LIST_HEAD(&tmp);
-	
+repeat:
 	spin_lock(&lru_list_lock);
 
 	while (!list_empty(list)) {
+		if (conditional_schedule_needed()) {
+			spin_unlock(&lru_list_lock);
+			unconditional_schedule();
+			goto repeat;
+		}
 		bh = BH_ENTRY(list->next);
 		list_del(&bh->b_inode_buffers);
 		if (!buffer_dirty(bh) && !buffer_locked(bh))
@@ -922,8 +958,18 @@
 				spin_lock(&lru_list_lock);
 			}
 		}
+		if (TEST_RESCHED_COUNT(32)) {
+			RESET_RESCHED_COUNT();
+			if (conditional_schedule_needed()) {
+				spin_unlock(&lru_list_lock);
+				unconditional_schedule();
+				spin_lock(&lru_list_lock);
+			}
+		}
 	}
 
+	RESET_RESCHED_COUNT();
+
 	while (!list_empty(&tmp)) {
 		bh = BH_ENTRY(tmp.prev);
 		remove_inode_queue(bh);
@@ -933,6 +979,7 @@
 		if (!buffer_uptodate(bh))
 			err = -EIO;
 		brelse(bh);
+		conditional_schedule();
 		spin_lock(&lru_list_lock);
 	}
 	
@@ -960,11 +1007,20 @@
 	struct buffer_head *bh;
 	struct list_head *p;
 	int err = 0;
+	DEFINE_RESCHED_COUNT;
 
+repeat:
+	conditional_schedule();
 	spin_lock(&lru_list_lock);