Re: 2.4.1pre8 slowdown on dbench tests

[Steven Cole]

On Tuesday 23 January 2001 13:54, Jens Axboe wrote:
>
> Thanks! Could I talk you into doing one last run? pre8 with
> include/linux/elevator.h having these values set for
> ELEVATOR_LINUS:
>
Here are two sets of dbench 48 runs with that mod. I can't explain why the
second set is faster.  The second set was performed with no reboot after the 
first set.  The individual runs were performed with no wait in-between.

Steven

2.4.1-pre8 with changes to elevator.h, first run set
average:   9.52569 MB/sec

Throughput 9.51356 MB/sec (NB=11.892 MB/sec  95.1356 MBit/sec)
Throughput 9.43096 MB/sec (NB=11.7887 MB/sec  94.3096 MBit/sec)
Throughput 9.54195 MB/sec (NB=11.9274 MB/sec  95.4195 MBit/sec)
Throughput 9.61631 MB/sec (NB=12.0204 MB/sec  96.1631 MBit/sec)

2.4.1-pre8 same as above, second run set
average:   10.1621 MB/sec

Throughput 10.1236 MB/sec (NB=12.6546 MB/sec  101.236 MBit/sec)
Throughput 10.0304 MB/sec (NB=12.5381 MB/sec  100.304 MBit/sec)
Throughput 10.1844 MB/sec (NB=12.7305 MB/sec  101.844 MBit/sec)
Throughput 10.3099 MB/sec (NB=12.8873 MB/sec  103.099 MBit/sec)

Here is the change I made to elevator.h which you suggested:

--- elevator.h.orig     Wed Jan 24 07:12:00 2001
+++ elevator.h  Wed Jan 24 07:12:47 2001
@@ -94,8 +94,8 @@
 
 #define ELEVATOR_LINUS                                                 \
 ((elevator_t) {                                                              
  \
-       8192,                           /* read passovers */            \
-       16384,                          /* write passovers */           \
+       1000000,                                /* read passovers */          
  \
+       2000000,                                /* write passovers */         
  \
                                                                        \
        elevator_linus_merge,           /* elevator_merge_fn */         \
        elevator_linus_merge_cleanup,   /* elevator_merge_cleanup_fn */ \