lk 2.5.3 scsi generic (sg) driver

In lk 2.5.3 the sg driver tries to set up both address and page+offset in scatterlist entries. Unfortunately asm-i386/pci.h's pci_map_sg() contains this check:

                if (sg[i].address && sg[i].page)
                        BUG();

which kills that strategy when the sym53c8xx driver uses pci_map_sg(). This patch has been posted earlier for lk 2.5.3-pre5 and is still required for lk 2.5.3

Doug Gilbert

@@ -19,7 +19,7 @@
  */
 #include <linux/config.h>
 #ifdef CONFIG_PROC_FS
- static char sg_version_str[] = "Version: 3.5.23 (20020103)";
+ static char sg_version_str[] = "Version: 3.5.23 (20020124)";
 #endif
  static int sg_version_num = 30523; /* 2 digits for each component */
 /*

@@ -76,7 +76,7 @@
 #include <linux/version.h>
 #endif /* LINUX_VERSION_CODE */
 
-#define SG_STILL_HAVE_ADDRESS_IN_SCATTERLIST
+/* #define SG_STILL_HAVE_ADDRESS_IN_SCATTERLIST */
 
 #define SG_ALLOW_DIO_DEF 0
 #define SG_ALLOW_DIO_CODE      /* compile out be commenting this define */

I'm trying to profile an application using the 'gprof' utility, and in particular get timing information from the profile.

For some reason, the output from gprof displays

"no time accumulated"

and I see no cumulative/self seconds at all. However, all of the call counts appear to be correct.

I suspect that the sampling rate using by gprof/linux is simply two slow, given the particular application I'm running.

Can anybody help me obtain timing information from gprof and/or point me to a better source for application profiling in general?

Thankyou for your support.
David Francheski

This is way OT for linux-kernel, but here goes:

If you application runs for a very short amount of time (say, less than a second) the profile will probably be dominated by glibc startup, application
initializations and exit routines. It's useless. That you don't have
time accumulated is the least of your problems - even with the times, your profile would be random numbers and random function names.

In order to profile *anything* - you should make sure that it runs for a while (I would say minutes at least, but it depends very much on the complexity of your application, eg. number of functions involved, and how their run-time is affected by data input and the environment (timing-sensitive threaded applications etc.)). You simply need a good data sample, otherwise any data you have will be dominated by noise, and your profile will be random.

If it's a very small computational routine, simply put it in a
for (int i = 0; i != 100000; i++) { ... }

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