[PATCH] lk 2.5.3 scsi generic (sg) driver

[PATCH] lk 2.5.3 scsi generic (sg) driver

[Douglas Gilbert]

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


--- linux/drivers/scsi/sg.c     Thu Jan 24 18:45:01 2002
+++ linux/drivers/scsi/sg.c3523 Thu Jan 24 20:53:28 2002
@@ -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 */

gprof / profiling support ?

[Dave Francheski]

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

Re: gprof / profiling support ?

[Jakob Østergaard]

On Tue, Feb 05, 2002 at 03:20:47PM -0800, Dave Francheski wrote:
> 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?

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++) { ... }

-- 
................................................................
:   jakob@unthought.net   : And I see the elder races,         :
:.........................: putrid forms of man                :
:   Jakob Østergaard      : See him rise and claim the earth,  :
:        OZ9ABN           : his downfall is at hand.           :
:.........................:............{Konkhra}...............: