Re: [RFC|PATCH] Compile time printk verbosity
On Tue, Sep 01, 2009 at 07:37:27PM -0400, Mike Frysinger wrote: 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. This won't work because it would for example also return from functions which call printk but aren't checking for the return value (which is the common case). Or am I missing something? -mike Marc -- Marc Andre Tanner http://www.brain-dump.org/ GPG key: CF7D56C0 -- 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 Wed, Sep 02, 2009 at 12:35:42AM +0100, Jamie Lokier wrote:
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.
Thanks, so if I understood it correctly this should be used like this:
#define PRINTK_FILTER(fmt) (
\
(((const char *)(fmt))[0] != '' CONFIG_PRINTK_VERBOSITY = 4) ||
\
(((const char *)(fmt))[0] == ''
\
((const char *)(fmt))[1] = *__stringify(CONFIG_PRINTK_VERBOSITY))
\
)
#define printk(fmt, ...) ({
\
if (__builtin_constant_p(PRINTK_FILTER(fmt)) PRINTK_FILTER(fmt))
\
printk((fmt), ##__VA_ARGS__);
\
})
The sizeof check wouldn't be necessary. Is this correct?
Marc
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Re: [PATCH 7/7] printk: provide a filtering macro for printk
On Tue, Sep 01, 2009 at 07:32:25PM -0400, H Hartley Sweeten wrote: On Tuesday, September 01, 2009 4:24 PM, Tim Bird wrote: 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? Yes it's true that KERN_CONT isn't handled correctly, but I don't see a way to change that. 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. $ grep -R KERN_CONT linux-2.6 | wc -l 373 Maybe another mechanism is needed to ensure that continuation printk lines have the same log level as their start strings. I currently don't see a way to achieve this with the CPP. But, overall, very slick! It's nice to see a solution that doesn't require changing all printks statements in the kernel. Yes that's what I thought too. Thanks to the comments so far the next version of the patch will contain even less changes to the rest of 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.)? It should work, yes. Regards, Marc -- Marc Andre Tanner http://www.brain-dump.org/ GPG key: CF7D56C0 -- 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
Mike Frysinger wrote:
it depends completely on how the macro is intended to be used. if you
want to maintain the this macro has a return value, then you have to
use ({...}). if you want the macro to return a void, then you have to
use do{...}while(0).
Actually no. The difference is do {...} while(0) is a _statement_ and
cannot be used in an expression. Whereas a void value can be used in
expressions like A?B:C, (A,B) and returned from a function, it just
has type void.
-- Jamie
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[PATCH 1/5] 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 | 29 + 1 files changed, 29 insertions(+), 0 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 3f7e609..549ed95 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -833,6 +833,35 @@ 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 listed below. Note that messages + without an explicit loglevel will be classified as KERN_WARNING. + + 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 2/5] 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
--
1.6.3.3
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[PATCH 4/5] char/mem: replace printk with printk_unfiltered
We don't want to filter user space data which comes from /dev/kmsg.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
drivers/char/mem.c |2 +-
1 files changed, 1 insertions(+), 1 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;
--
1.6.3.3
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[PATCH 5/5] printk: provide a filtering macro for printk
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 | 23 +++ 1 files changed, 23 insertions(+), 0 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index c2b3047..1ecc338 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -242,6 +242,29 @@ 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. + */ + +#include linux/stringify.h + +#define PRINTK_FILTER(fmt) ( \ + (((const char *)(fmt))[0] != '' CONFIG_PRINTK_VERBOSITY = 4) || \ + (((const char *)(fmt))[0] == '' \ +((const char *)(fmt))[1] = *__stringify(CONFIG_PRINTK_VERBOSITY)) \ +) + +#define printk(fmt, ...) ( \ + (!__builtin_constant_p(PRINTK_FILTER((fmt))) || PRINTK_FILTER((fmt))) ? \ + printk((fmt), ##__VA_ARGS__) : 0 \ +) + +#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, -- 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 3/5] printk: introduce printk_unfiltered as an alias to printk
The standard printk function will be wrapped by a macro which
filters out messages above a certain verbosity level. Because
this might not be desired in certain situations we provide an
unfiltered variant.
Signed-off-by: Marc Andre Tanner m...@brain-dump.org
---
include/linux/kernel.h |5 +
kernel/printk.c| 23 +++
2 files changed, 28 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..0a2f654 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 which will filter out messages above a certain verbosity level.
+ * In cases where it's important that the message will get through independenly
+ * of the configuration setting printk_unfiltered 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 +1351,14 @@ asmlinkage int printk(const char *fmt, ...)
return r;
}
EXPORT_SYMBOL(printk);
+
+/*
+ * Because printk might be wrapped by a macro which will filter out messages
+ * above a certain verbosity level we provide an unfiltered variant for use
+ * cases where the filtering isn't desired.
+ */
+
+asmlinkage int printk_unfiltered(const char *fmt, ...)
+ __attribute__((alias(printk)));
+EXPORT_SYMBOL(printk_unfiltered);
#endif
--
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Re: [PATCH 1/5] printk: introduce CONFIG_PRINTK_VERBOSITY
Marc Andre Tanner ha scritto: 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 | 29 + 1 files changed, 29 insertions(+), 0 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 3f7e609..549ed95 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -833,6 +833,35 @@ 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 listed below. Note that messages + without an explicit loglevel will be classified as KERN_WARNING. + +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 If there are some problems to handle KERN_CONT you should say something here. You should even add in cc: the kernel ML, however it seems a good work. Marco -- 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 1/5] printk: introduce CONFIG_PRINTK_VERBOSITY
On Wed, Sep 02, 2009 at 06:44:06PM +0200, Marco Stornelli wrote: Marc Andre Tanner ha scritto: 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 | 29 + 1 files changed, 29 insertions(+), 0 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 3f7e609..549ed95 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -833,6 +833,35 @@ 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 listed below. Note that messages + without an explicit loglevel will be classified as KERN_WARNING. + + 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 If there are some problems to handle KERN_CONT you should say something here. ACK. You should even add in cc: the kernel ML, however it seems a good work. Well I first wanted to get some feedback from the embedded people. I will probably send it to LKML after the 2.6.31 release, don't know how the chances for inclusion are though. Marc -- Marc Andre Tanner http://www.brain-dump.org/ GPG key: CF7D56C0 -- 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: 100Mbit ethernet performance on embedded devices
Johannes Stezenbach wrote: 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? I have a pico station, http://ubnt.com/products/picostation.php with Atheros MIPS 4KC @ 180MHz. Iperf on this device gives 46.0 Mbits/sec sending TCP from a PC to the device and 36.2 Mbits/sec sending TCP from the device to a PC. The NIC is part of the Atheros chipset so PCI is not involved. -ack -- 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
