Re: Linux 2.6.6 "IDE cache-flush at shutdown fixes"

[Rene Herman]

Bartlomiej Zolnierkiewicz wrote:

> > Vanilla 2.6.6:
> >
> > rene@7ixe4:~/cache$ grep wcache settings-2.6.6
> > wcache                  1               0               1               rw
> >
> > 2.6.6 with the de{flush,spin}ification patches:
> >
> > rene@7ixe4:~/cache$ grep wcache settings-2.6.6-hackedup
> > wcache                  0               0               1               rw
> >
> > Hrmpf. 0?
>
> Very interesting, can you try vanilla 2.6.5 (or some other 2.6.x)?

2.4.26		: wcache = 0, 0, 1
2.6.6-rc3-mm2	: wcache = 0, 0, 1
2.6.6		: wcache = 1, 0, 1
2.6.6-hackedup	: wcache = 0, 0, 1

(on none of these hdparm -W0/1 has any effect, by the way)

> We are getting close to the real problem.

Indeed. I have attached two "tiobench" seq. write results, one for 
vanilla 2.6.6, and one for 2.6.6-hackedup (your changes). I remember the 
result for the latter are the normal ones I got with previous kernels as 
well. The differences are very interesting.

2.6.6-vanilla (ie, the one showing wcache=1): +/- 10MB/s
2.6.6-hackedup (ie, shows wcache=0)	    : +/- 46MB/s

As said, that 46 is the expected value. Is this a logic inversion bug in 
either driver (but then both 2.4.26 and 2.6) or drive firmware?

Rene.

Sequential Writes
                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----
2.6.6                         1534  4096    1   10.74 9.440%     0.298     2641.08   0.00102  0.00000   114
2.6.6                         1534  4096    2   10.64 9.999%     0.586     7005.74   0.00331  0.00000   106
2.6.6                         1534  4096    4   10.64 9.730%     1.129    17964.34   0.02550  0.00025   109
2.6.6                         1534  4096    8   10.12 9.423%     2.099    28425.08   0.04065  0.00256   107
Sequential Writes
                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----
2.6.6                         1534  4096    1   46.59 57.01%     0.069      598.21   0.00000  0.00000    82
2.6.6                         1534  4096    2   42.44 50.34%     0.155     1951.60   0.00000  0.00000    84
2.6.6                         1534  4096    4   44.65 52.23%     0.267     1336.76   0.00000  0.00000    85
2.6.6                         1534  4096    8   37.78 41.34%     0.604     6720.81   0.00307  0.00000    91