[RFC|PATCH] Compile time printk verbosity
This series adds a configuration option to selectively compile out printk message strings based on a verbosity level. This works by wrapping printk with a macro which evaluates to a constant if condition which the compiler will be able to optimize out. However because printk might be wrapped by a macro it no longer has a return value. This means that constructs like the following ones don't work: ((void)(SOME_RANDOM_DEBUG_FLAG printk(...)); some_random_variable = printk(...); Therefore printk_unfiltered is introduced which is just an alias to the standard printk function but not wrapped by a macro. Patches 4-6 make existing kernel code aware of this fact. The series was compile tested with make allyesconfig for x86 and arm (with a cross compiler) but I might have missed something. All kinds of comments are welcome. Marc Andre Tanner (7): printk: introduce CONFIG_PRINTK_VERBOSITY printk: move printk to the end of the file printk: introduce printk_unfiltered as an alias to printk drivers: replace printk with printk_unfiltered drivers: make macro independent of printk's return value video/stk-webcam: change use of STK_ERROR printk: provide a filtering macro for printk drivers/char/mem.c |2 +- drivers/md/md.c|2 +- drivers/md/raid5.c |2 +- drivers/media/video/stk-webcam.c | 16 +++--- drivers/net/e100.c |2 +- drivers/net/ixgb/ixgb.h|2 +- drivers/net/ixgbe/ixgbe.h |2 +- drivers/scsi/aic7xxx/aic79xx_osm.h |2 +- drivers/scsi/aic7xxx/aic7xxx_osm.h |2 +- include/linux/kernel.h | 29 +++ include/net/sctp/sctp.h|2 +- init/Kconfig | 28 ++ kernel/lockdep.c |4 +- kernel/printk.c| 96 +++- 14 files changed, 137 insertions(+), 54 deletions(-) -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH 5/7] drivers: make macro independent of printk's return value
Because printk might be wrapped by a macro avoid constructs which
assume that the return value can be interpreted as a boolean value.
This doesn't work because the macro has no return value which
results in a compile error void value not ignored as it ought to be.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
drivers/md/raid5.c|2 +-
drivers/net/e100.c|2 +-
drivers/net/ixgb/ixgb.h |2 +-
drivers/net/ixgbe/ixgbe.h |2 +-
include/net/sctp/sctp.h |2 +-
5 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b8a2c5d..d0dac07 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -92,7 +92,7 @@
#define __inline__
#endif
-#define printk_rl(args...) ((void) (printk_ratelimit() printk(args)))
+#define printk_rl(args...) ((void)(!printk_ratelimit() ?: printk(args)))
/*
* We maintain a biased count of active stripes in the bottom 16 bits of
diff --git a/drivers/net/e100.c b/drivers/net/e100.c
index 3a6735d..3598d49 100644
--- a/drivers/net/e100.c
+++ b/drivers/net/e100.c
@@ -199,7 +199,7 @@ MODULE_PARM_DESC(debug, Debug level (0=none,...,16=all));
MODULE_PARM_DESC(eeprom_bad_csum_allow, Allow bad eeprom checksums);
MODULE_PARM_DESC(use_io, Force use of i/o access mode);
#define DPRINTK(nlevel, klevel, fmt, args...) \
- (void)((NETIF_MSG_##nlevel nic-msg_enable) \
+ (void)(!(NETIF_MSG_##nlevel nic-msg_enable) ?: \
printk(KERN_##klevel PFX %s: %s: fmt, nic-netdev-name, \
__func__ , ## args))
diff --git a/drivers/net/ixgb/ixgb.h b/drivers/net/ixgb/ixgb.h
index d85717e..5208677 100644
--- a/drivers/net/ixgb/ixgb.h
+++ b/drivers/net/ixgb/ixgb.h
@@ -83,7 +83,7 @@ struct ixgb_adapter;
#define PFX ixgb:
#define DPRINTK(nlevel, klevel, fmt, args...) \
- (void)((NETIF_MSG_##nlevel adapter-msg_enable) \
+ (void)(!(NETIF_MSG_##nlevel adapter-msg_enable) ?: \
printk(KERN_##klevel PFX %s: %s: fmt, adapter-netdev-name, \
__func__ , ## args))
diff --git a/drivers/net/ixgbe/ixgbe.h b/drivers/net/ixgbe/ixgbe.h
index 2c4dc82..eb67b31 100644
--- a/drivers/net/ixgbe/ixgbe.h
+++ b/drivers/net/ixgbe/ixgbe.h
@@ -46,7 +46,7 @@
#define PFX ixgbe:
#define DPRINTK(nlevel, klevel, fmt, args...) \
- ((void)((NETIF_MSG_##nlevel adapter-msg_enable) \
+ ((void)(!(NETIF_MSG_##nlevel adapter-msg_enable) ?: \
printk(KERN_##klevel PFX %s: %s: fmt, adapter-netdev-name, \
__func__ , ## args)))
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index d16a304..c13fcf9 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -276,7 +276,7 @@ struct sctp_mib {
#if SCTP_DEBUG
extern int sctp_debug_flag;
#define SCTP_DEBUG_PRINTK(whatever...) \
- ((void) (sctp_debug_flag printk(KERN_DEBUG whatever)))
+ ((void) (!sctp_debug_flag ?: printk(KERN_DEBUG whatever)))
#define SCTP_DEBUG_PRINTK_IPADDR(lead, trail, leadparm, saddr, otherparms...) \
if (sctp_debug_flag) { \
if (saddr-sa.sa_family == AF_INET6) { \
--
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[PATCH 1/7] printk: introduce CONFIG_PRINTK_VERBOSITY
Introduce a config option which allows to selectively compile out printk messages based on a specified verbosity level. Signed-off-by: Marc Andre Tanner m...@brain-dump.org --- init/Kconfig | 28 1 files changed, 28 insertions(+), 0 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 3f7e609..3618168 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -833,6 +833,34 @@ config PRINTK very difficult to diagnose system problems, saying N here is strongly discouraged. +config PRINTK_VERBOSITY + int Printk compile time verbosity + depends on EMBEDDED PRINTK + range 0 7 + default 0 + help + + Select the maximum printk verbosity level to be compiled into + the kernel. + + Messages above the specified verbosity level are removed from + the kernel at compile time. This reduces the kernel image size + at the cost of a calmer kernel. + + Possible verbosity levels are: + + 0 Disable this feature and compile all messages in. + + 1 KERN_ALERT/* action must be taken immediately */ + 2 KERN_CRIT /* critical conditions */ + 3 KERN_ERR /* error conditions */ + 4 KERN_WARNING /* warning conditions*/ + 5 KERN_NOTICE /* normal but significant condition */ + 6 KERN_INFO /* informational */ + 7 KERN_DEBUG/* debug-level messages */ + + If unsure, just move on and leave this option alone. + config BUG bool BUG() support if EMBEDDED default y -- 1.6.3.3 -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH 6/7] video/stk-webcam: change use of STK_ERROR
Don't rely on the return value of STK_ERROR which is a wrapper
around printk use a normal if clause instead.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
drivers/media/video/stk-webcam.c | 16
1 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/media/video/stk-webcam.c b/drivers/media/video/stk-webcam.c
index b154bd9..ea7e70e 100644
--- a/drivers/media/video/stk-webcam.c
+++ b/drivers/media/video/stk-webcam.c
@@ -386,8 +386,8 @@ static void stk_isoc_handler(struct urb *urb)
if (list_empty(dev-sio_avail)) {
/*FIXME Stop streaming after a while */
- (void) (printk_ratelimit()
- STK_ERROR(isoc_handler without available buffer!\n));
+ if (printk_ratelimit())
+ STK_ERROR(isoc_handler without available buffer!\n);
goto resubmit;
}
fb = list_first_entry(dev-sio_avail,
@@ -422,10 +422,10 @@ static void stk_isoc_handler(struct urb *urb)
/* This marks a new frame */
if (fb-v4lbuf.bytesused != 0
fb-v4lbuf.bytesused != dev-frame_size) {
- (void) (printk_ratelimit()
- STK_ERROR(frame %d,
- bytesused=%d, skipping\n,
- i, fb-v4lbuf.bytesused));
+ if (printk_ratelimit())
+ STK_ERROR(frame %d,
+ bytesused=%d, skipping\n,
+ i, fb-v4lbuf.bytesused);
fb-v4lbuf.bytesused = 0;
fill = fb-buffer;
} else if (fb-v4lbuf.bytesused == dev-frame_size) {
@@ -450,8 +450,8 @@ static void stk_isoc_handler(struct urb *urb)
/* Our buffer is full !!! */
if (framelen + fb-v4lbuf.bytesused dev-frame_size) {
- (void) (printk_ratelimit()
- STK_ERROR(Frame buffer overflow, lost sync\n));
+ if (printk_ratelimit())
+ STK_ERROR(Frame buffer overflow, lost sync\n);
/*FIXME Do something here? */
continue;
}
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[PATCH 4/7] drivers: replace printk with printk_unfiltered
Use the unfiltered variant in cases where the return value
is of interest.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
drivers/char/mem.c |2 +-
drivers/md/md.c|2 +-
drivers/scsi/aic7xxx/aic79xx_osm.h |2 +-
drivers/scsi/aic7xxx/aic7xxx_osm.h |2 +-
kernel/lockdep.c |4 ++--
5 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index afa8813..ba48b82 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -850,7 +850,7 @@ static ssize_t kmsg_write(struct file * file, const char
__user * buf,
ret = -EFAULT;
if (!copy_from_user(tmp, buf, count)) {
tmp[count] = 0;
- ret = printk(%s, tmp);
+ ret = printk_unfiltered(%s, tmp);
if (ret count)
/* printk can add a prefix */
ret = count;
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9dd8720..85c31bf 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -51,7 +51,7 @@
#include bitmap.h
#define DEBUG 0
-#define dprintk(x...) ((void)(DEBUG printk(x)))
+#define dprintk(x...) ((void)(DEBUG printk_unfiltered(x)))
#ifndef MODULE
diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.h
b/drivers/scsi/aic7xxx/aic79xx_osm.h
index 55c1fe0..65a30c5 100644
--- a/drivers/scsi/aic7xxx/aic79xx_osm.h
+++ b/drivers/scsi/aic7xxx/aic79xx_osm.h
@@ -364,7 +364,7 @@ struct ahd_platform_data {
};
/** OS Utility Wrappers
***/
-#define printf printk
+#define printf printk_unfiltered
#define M_NOWAIT GFP_ATOMIC
#define M_WAITOK 0
#define malloc(size, type, flags) kmalloc(size, flags)
diff --git a/drivers/scsi/aic7xxx/aic7xxx_osm.h
b/drivers/scsi/aic7xxx/aic7xxx_osm.h
index 56f07e5..cf05c2b 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_osm.h
+++ b/drivers/scsi/aic7xxx/aic7xxx_osm.h
@@ -369,7 +369,7 @@ struct ahc_platform_data {
};
/** OS Utility Wrappers
***/
-#define printf printk
+#define printf printk_unfiltered
#define M_NOWAIT GFP_ATOMIC
#define M_WAITOK 0
#define malloc(size, type, flags) kmalloc(size, flags)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 8bbeef9..154756a 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -564,8 +564,8 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
if (class-usage_mask (1 bit)) {
int len = depth;
- len += printk(%*s %s, depth, , usage_str[bit]);
- len += printk( at:\n);
+ len += printk_unfiltered(%*s %s, depth, ,
usage_str[bit]);
+ len += printk_unfiltered( at:\n);
print_stack_trace(class-usage_traces + bit, len);
}
}
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[PATCH 2/7] printk: move printk to the end of the file
A later patch will #undef printk because the macro would otherwise
conflict with the function definition. Moving the printk function
to the end of the file makes sure that the macro is expanded within
the rest of the file.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
kernel/printk.c | 72 --
1 files changed, 37 insertions(+), 35 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index b4d97b5..5455d41 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -551,40 +551,6 @@ static int have_callable_console(void)
return 0;
}
-/**
- * printk - print a kernel message
- * @fmt: format string
- *
- * This is printk(). It can be called from any context. We want it to work.
- *
- * We try to grab the console_sem. If we succeed, it's easy - we log the
output and
- * call the console drivers. If we fail to get the semaphore we place the
output
- * into the log buffer and return. The current holder of the console_sem will
- * notice the new output in release_console_sem() and will send it to the
- * consoles before releasing the semaphore.
- *
- * One effect of this deferred printing is that code which calls printk() and
- * then changes console_loglevel may break. This is because console_loglevel
- * is inspected when the actual printing occurs.
- *
- * See also:
- * printf(3)
- *
- * See the vsnprintf() documentation for format string extensions over C99.
- */
-
-asmlinkage int printk(const char *fmt, ...)
-{
- va_list args;
- int r;
-
- va_start(args, fmt);
- r = vprintk(fmt, args);
- va_end(args);
-
- return r;
-}
-
/* cpu currently holding logbuf_lock */
static volatile unsigned int printk_cpu = UINT_MAX;
@@ -770,7 +736,6 @@ out_restore_irqs:
preempt_enable();
return printed_len;
}
-EXPORT_SYMBOL(printk);
EXPORT_SYMBOL(vprintk);
#else
@@ -1337,3 +1302,40 @@ bool printk_timed_ratelimit(unsigned long
*caller_jiffies,
}
EXPORT_SYMBOL(printk_timed_ratelimit);
#endif
+
+#ifdef CONFIG_PRINTK
+/**
+ * printk - print a kernel message
+ * @fmt: format string
+ *
+ * This is printk(). It can be called from any context. We want it to work.
+ *
+ * We try to grab the console_sem. If we succeed, it's easy - we log the
output and
+ * call the console drivers. If we fail to get the semaphore we place the
output
+ * into the log buffer and return. The current holder of the console_sem will
+ * notice the new output in release_console_sem() and will send it to the
+ * consoles before releasing the semaphore.
+ *
+ * One effect of this deferred printing is that code which calls printk() and
+ * then changes console_loglevel may break. This is because console_loglevel
+ * is inspected when the actual printing occurs.
+ *
+ * See also:
+ * printf(3)
+ *
+ * See the vsnprintf() documentation for format string extensions over C99.
+ */
+
+asmlinkage int printk(const char *fmt, ...)
+{
+ va_list args;
+ int r;
+
+ va_start(args, fmt);
+ r = vprintk(fmt, args);
+ va_end(args);
+
+ return r;
+}
+EXPORT_SYMBOL(printk);
+#endif
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[PATCH 3/7] printk: introduce printk_unfiltered as an alias to printk
The standard printk function will be wrapped by a macro.
However this doesn't work in all situations (for example
when the return value of printk is of interest). We
therefore provide a new function which is just an alias
to printk and therefore bypasses the macro.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
include/linux/kernel.h |5 +
kernel/printk.c| 24
2 files changed, 29 insertions(+), 0 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d6320a3..c2b3047 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -239,6 +239,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
__attribute__ ((format (printf, 1, 0)));
asmlinkage int printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2))) __cold;
+asmlinkage int printk_unfiltered(const char *fmt, ...)
+ __attribute__ ((format (printf, 1, 2))) __cold;
extern struct ratelimit_state printk_ratelimit_state;
extern int printk_ratelimit(void);
@@ -265,6 +267,9 @@ static inline int vprintk(const char *s, va_list args) {
return 0; }
static inline int printk(const char *s, ...)
__attribute__ ((format (printf, 1, 2)));
static inline int __cold printk(const char *s, ...) { return 0; }
+static inline int printk_unfiltered(const char *s, ...)
+ __attribute__ ((format (printf, 1, 2)));
+static inline int __cold printk_unfiltered(const char *s, ...) { return 0; }
static inline int printk_ratelimit(void) { return 0; }
static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \
unsigned int interval_msec) \
diff --git a/kernel/printk.c b/kernel/printk.c
index 5455d41..20379b5 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1310,6 +1310,11 @@ EXPORT_SYMBOL(printk_timed_ratelimit);
*
* This is printk(). It can be called from any context. We want it to work.
*
+ * Note that depending on the kernel configuration printk might be wrapped by
+ * a macro. In cases where it's important that the implementation is a function
+ * (for example when the return value of printk is of interest)
printk_unfiltered
+ * which bypasses the macro should be used instead.
+ *
* We try to grab the console_sem. If we succeed, it's easy - we log the
output and
* call the console drivers. If we fail to get the semaphore we place the
output
* into the log buffer and return. The current holder of the console_sem will
@@ -1326,6 +1331,14 @@ EXPORT_SYMBOL(printk_timed_ratelimit);
* See the vsnprintf() documentation for format string extensions over C99.
*/
+/*
+ * We need to #undef the printk macro from linux/kernel.h because
+ * it would otherwise conflict with the function implementation.
+ */
+#ifdef printk
+# undef printk
+#endif
+
asmlinkage int printk(const char *fmt, ...)
{
va_list args;
@@ -1338,4 +1351,15 @@ asmlinkage int printk(const char *fmt, ...)
return r;
}
EXPORT_SYMBOL(printk);
+
+/*
+ * Because printk might be wrapped by a macro which doesn't work in all
+ * circumstances (for example when the return value of printk is of
+ * interest) we make the functionality also available as a normal
+ * function.
+ */
+
+asmlinkage int printk_unfiltered(const char *fmt, ...)
+ __attribute__((alias(printk)));
+EXPORT_SYMBOL(printk_unfiltered);
#endif
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Re: [PATCH 7/7] printk: provide a filtering macro for printk
Marc Andre Tanner wrote: + * The check with sizeof(void*) should make sure that we don't operate on + * pointers, which the compiler wouldn't be able to optimize out, but only + * on string constants. Take a look at __builtin_constant_p in the GCC manual. You'll probably find that wrapping the whole of the rest of the expression (without the sizeof) in __builtin_constant_p is a good way to know when to depend on the result of the expression. -- Jamie -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC|PATCH] Compile time printk verbosity
On Tue, Sep 1, 2009 at 18:31, Marc Andre Tanner wrote: This series adds a configuration option to selectively compile out printk message strings based on a verbosity level. This works by wrapping printk with a macro which evaluates to a constant if condition which the compiler will be able to optimize out. However because printk might be wrapped by a macro it no longer has a return value. This means that constructs like the following ones don't work: ((void)(SOME_RANDOM_DEBUG_FLAG printk(...)); some_random_variable = printk(...); Therefore printk_unfiltered is introduced which is just an alias to the standard printk function but not wrapped by a macro. why dont you return 0 if it gets optimized away ? then you wont have to screw with external code at all and things just work. -mike -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH 7/7] printk: provide a filtering macro for printk
On Tuesday, September 01, 2009 4:24 PM, Tim Bird wrote:
Marc Andre Tanner wrote:
The macro filters out printk messages based on a configurable verbosity
level (CONFIG_PRINTK_VERBOSITY).
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
include/linux/kernel.h | 24
1 files changed, 24 insertions(+), 0 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index c2b3047..1f5d01f 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -242,6 +242,30 @@ asmlinkage int printk(const char * fmt, ...)
asmlinkage int printk_unfiltered(const char *fmt, ...)
__attribute__ ((format (printf, 1, 2))) __cold;
+#if defined(CONFIG_PRINTK_VERBOSITY) CONFIG_PRINTK_VERBOSITY 0
+/*
+ * The idea here is to wrap the actual printk function with a macro which
+ * will filter out all messages above a certain verbosity level. Because
+ * the if condition evaluates to a constant expression the compiler will be
+ * able to eliminate it and the resulting kernel image will be smaller.
+ *
+ * The check with sizeof(void*) should make sure that we don't operate on
+ * pointers, which the compiler wouldn't be able to optimize out, but only
+ * on string constants.
+ */
+
+#include linux/stringify.h
+
+#define printk(fmt, ...) ({
\
+if (sizeof(fmt) == sizeof(void *) ||
\
+(((const char *)(fmt))[0] != '' CONFIG_PRINTK_VERBOSITY = 4)
|| \
+(((const char *)(fmt))[0] == ''
\
+ ((const char *)(fmt))[1] =
*__stringify(CONFIG_PRINTK_VERBOSITY))) \
+printk((fmt), ##__VA_ARGS__);
\
+})
+
+#endif /* CONFIG_PRINTK_VERBOSITY */
+
extern struct ratelimit_state printk_ratelimit_state;
extern int printk_ratelimit(void);
extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
Some places in the kernel break the message into pieces, like so:
printk(KERN_ERR, Error: first part );
...
printk( more info for error.\n);
Technically, shouldn't the second part of the message actually be:
printk(KERN_CONT more info for error.\n);
Maybe some mechanism could be created to handle the continued message
if they have the KERN_CONT?
These parts would not be handled consistently under certain
conditions.
It would be confusing to see only part of the message,
but I don't know how often this construct is used. Maybe
another mechanism is needed to ensure that continuation
printk lines have the same log level as their start strings.
But, overall, very slick! It's nice to see a solution that doesn't
require changing all printks statements in the kernel.
I haven't looked over this patch series yet but does it work with the
pr_level macros (pr_info, pr_err, etc.)?
Regards,
Hartley
Re: 100Mbit ethernet performance on embedded devices
On Thu, Aug 20, 2009 at 12:50 AM, Johannes Stezenbach j...@sig21.net wrote: Hi, a while ago I was working on a SoC with 200MHz ARM926EJ-S CPU and integrated 100Mbit ethernet core, connected on internal (fast) memory bus, with DMA. With iperf I measured: TCP RX ~70Mbit/sec (iperf -s on SoC, iperf -c on destop PC) TCP TX ~56Mbit/sec (iperf -s on destop PC, iperf -c o SoC) What I'm interested in are some numbers for similar hardware, to find out if my hardware and/or ethernet driver can be improved, or if the CPU will always be the limiting factor. I'd also be interested to know if hardware checksumming support would improve throughput noticably in such a system, or if it is only useful for 1Gbit and above. Did anyone actually manage to get close to 100Mbit/sec with similar CPU resources? No, but I can share results. AT91RM9200 (ARM920T), 180MHz Davicom 9161 PHY Linux 2.6.26.3 CONFIG_NETFILTER=y CONFIG_NETFILTER_ADVANCED=y # uptime; iperf -s; uptime 00:07:33 up 7 min, load average: 0.02, 0.10, 0.07 Server listening on TCP port 5001 TCP window size: 85.3 KByte (default) [ 4] local 169.254.0.235 port 5001 connected with 169.254.0.2 port 50762 [ ID] Interval Transfer Bandwidth [ 4] 0.0-10.0 sec 58.6 MBytes 49.1 Mbits/sec 00:07:46 up 7 min, load average: 0.17, 0.13, 0.08 -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
