Re: 1352 NUL bytes at the end of a page? (was Re: Assertion `s && s->tree' failed: The saga continues.)

[Steven Cole <elenstev@mesatop.com>]

On Sunday 16 May 2004 04:01 am, Andrew Morton wrote:
> Steven Cole <elenstev@mesatop.com> wrote:
> >
> > The script only reported one
> >  iteration finished, while I got it to do 36 iterations over several hours earlier
> >  today (with a 2.6.3-4mdk vendor kernel), so I'm going to add some timing 
> >  tests to the script to see if things are really slowing down with current kernels,
> >  or if it's just my worried imaginings.
> 
> I did a bit of testing on a 256MB laptop with a fairly slow disk, ext3. 
> Three iterations of the test took:
> 
> 2.6.6:		1055.53s user 327.14s system 32% cpu 1:10:06.71 total
> 
> 2.4.27-pre2:	1042.03s user 307.21s system 32% cpu 1:09:46.00 total
> 
> 2.6.3:		1053.23s user 326.16s system 27% cpu 1:22:07.24 total
> 
> 
> So there's nothing particularly wild there.  It's possible I guess that the
> 2.6 VM is very sucky but something else made up for it - possibly the
> anticipatory scheduler but more likely the Orlov allocator.
> 
> You're using reiserfs, yes?

Yes, but I also have a BK repo on an ext3 fs which saw the exact
same initial problem.  Well, almost in that I got the  Assertion `s && s->tree' failed
message, but didn't preserve the possibly null-containing s.ChangeSet file.

> 
> Are you sure the IDE disks are in DMA mode?
> 
> 
For the 2.6.3 tests, yes.
For the overnight 2.6.6 tests, apparently not, but it is now.
Without DMA, the clone took about 22 minutes, but even with
DMA back on, 2.6.6-current is much slower than 2.6.3-4mdk.

It's hard to make your wheels fall off when putting around the
race track at 2/3 speed.  If I get time, I'll try the patch from Nick
and/or a kernel from around 4/15 when I first saw this problem,
but the weather's nice outside, so it may be later this evening
before I return to testing.

/dev/hda:
 multcount    =  0 (off)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 65535/16/63, sectors = 78125000, start = 0

----------------------------
2.6.3-4mdk:

time bk clone -qlr40514130hBbvgP4CvwEVEu27oxm46w testing-2.6 foo
287.93user 59.33system 11:14.03elapsed 51%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (41264major+523595minor)pagefaults 0swaps

(cd foo; time bk pull -q)
397.05user 184.05system 16:38.35elapsed 58%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (30287major+2115127minor)pagefaults 0swaps
-----------------------------

-----------------------------
2.6.6-current:

time bk clone -qlr40514130hBbvgP4CvwEVEu27oxm46w testing-2.6 foo
290.48user 96.76system 15:00.85elapsed 42%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (50893major+515118minor)pagefaults 0swaps

(cd foo; time bk pull -q)
402.74user 254.98system 23:25.43elapsed 46%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (60130major+2089908minor)pagefaults 0swaps

------------------------------

Steven