Re: hyperthreading performance with dbt-2 on 2.6.0-test11

[Mark Wong]

Oops, sorry, I must of overlooked it because it looked like garbage.  Um, I'll
copy it anyway just in case it helps, but it didn't echo cleanly for some
reason:

<4>>UU:b e 4                           
 aF AGSr u7f e0d0ress P00s03t80xe eainredc
  pcinci8 g eip::00000002 0 espo ince: cd11e1fbr  cdx<40 a00v60t
                              : f5c41d04
0d0:                                    
     000   es: 0000   ss: 0068


On Tue, Dec 09, 2003 at 02:27:57PM +1100, Nick Piggin wrote:
> 
> 
> Mark Wong wrote:
> 
> >On Tue, Dec 09, 2003 at 11:17:26AM +1100, Nick Piggin wrote:
> >
> >>
> >>markw@xxxxxxxx wrote:
> >>
> >>
> >>>Hello, I have some data with hyperthreading I wanted to share.
> >>>
> >>>I've seen about a 15% performance decrease in performance on a 4-way
> >>>Xeon system when I enable hyperthreading for my DBT-2 workload.  I also
> >>>gave Ingo's test11-C1 patch that someone pointed me to a try and only
> >>>saw a 12% decrease. Has anyone found this to be common with any specific
> >>>workloads?
> >>>
> >>>I'm not really sure what to look for, but I do see some changes in the
> >>>readprofile data, which I've copied in part below.  It appears that the
> >>>count of schedule, __make_request, and try_to_wake_up are the only
> >>>functions at the top of the profile that are significantly different.
> >>>The links I have posted also have pointers to oprofile data as well as
> >>>annotated assembly source output, if that interests anyone.  If I can
> >>>provide any other details, let me know.
> >>>
> >>>
> >>Hi Mark,
> >>It could be cache contention which I think is typically the reason
> >>hyperthreading can hurt performance. Its basically impossible for
> >>the scheduler to correct this automatically (access to performance
> >>counters might make it slightly less impossible).
> >>
> >>Probably the CPU hotplug interface would enable a tool to effectively
> >>turn HT on or off and it would be up to an administrator to tune
> >>performance.
> >>
> >>You could try my scheduler patchset if you like. I have recently got
> >>HT support working (its against test11, you need to turn CONFIG_SMT
> >>on), although if Ingo's patch doesn't help much, mine probably won't
> >>either.
> >>
> >
> >Hi Nick,
> >
> >Went ahead and tried your patch, but it looks like something's wrong.  If
> >this helps any:
> >
> 
> Doh. OK, did you manage to capture anything above this?
> 
> >
> >Process postmaster (pid: 1086, threadinfo=f5c40000 task=f5c586b0)
> >Stack: f5c5007b 0000007b ffffffff c011f488 00000060 00010046 00000005 c322ccc0 
> >       c322c060 00000002 f5c5bdbc f686cb90 f686cb90 f5c41d4c f7f93940 f5ca6080 
> >       00000007 00000000 c322ccc0 00006f12 03d99f34 0000033d f5c586b0 f5c41dbc 
> >Call Trace:                                                                      [<c011f488>] schedule+0x380/0x705
> > [<c01ff412>] sys_semtimedop+0x460/0x530
> > [<c011e5bb>] find_busiest_group+0x2bc/0x2e3
> > [<c02c69ea>] p4_check_ctrs+0xab/0x11b      
> > [<c011e5bb>] find_busiest_group+0x2bc/0x2e3
> > [<c02c5a5d>] nmi_callback+0x25/0x29        
> > [<c014218d>] buffered_rmqueue+0xea/0x199
> > [<c010b8f5>] nmi_stack_correct+0x1e/0x2e
> > [<c01422eb>] __alloc_pages+0xaf/0x334   
> > [<c014007b>] generic_file_aio_write_nolock+0x298/0xa9e
> > [<c014d0c2>] do_anonymous_page+0x16a/0x28b            
> > [<c014d80b>] handle_mm_fault+0x101/0x1ad  
> > [<c011c4f5>] do_page_fault+0x2fa/0x4fc  
> > [<c011eb6d>] rebalance_tick+0x8a/0x91 
> > [<c02c4368>] oprofile_add_sample+0x9b/0x117
> > [<c02c69ea>] p4_check_ctrs+0xab/0x11b      
> > [<c0111ec4>] sys_ipc+0x61/0x2ae      
> > [<c02c5a5d>] nmi_callback+0x25/0x29
> > [<c010c839>] do_nmi+0x39/0x5a      
> > [<c010ad4d>] sysenter_past_esp+0x52/0x71
> >                                         
> >Code:  Bad EIP value.
> >
> >
> >
> >  
> >

-- 
Mark Wong - - markw@xxxxxxxx
Open Source Development Lab Inc - A non-profit corporation
12725 SW Millikan Way - Suite 400 - Beaverton, OR 97005
(503) 626-2455 x 32 (office)
(503) 626-2436      (fax)
http://developer.osdl.org/markw/
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