Re: [Iometer-user] IOMeter Workers under different managers usethe same location for Random read/write.

[Ming Z. <mi...@el...>]

On Mon, 2006-10-30 at 19:18 -0700, Liang Yang wrote:
> Hi Ming,
> 
> Running multiple managers (each manager has maximum 2 workers) is a 
> workaround to solve the serialized outstanding I/O issue for IOMeter using 
> O_DIRECT.However, this workaround does get cache involved for both 
> sequential and random operations.

ic. 

> 
> So I still prefer removing O_DIRECT.

currently, u can remove it via modifying the source code directly. i
will add this as run time option later. 

> 
> The reason I post here is I still think IOMeter shoud broadcast unique 
> random number to different managers no matter they are running on the same 
> machine or different machines.

agree, at least for disk target.

ps, did u fine time to test the patch for that cpu #?


> 
> Regards,
> 
> Liang
> 
> ----- Original Message ----- 
> From: "Ming Zhang" <mi...@el...>
> To: "Liang Yang" <mul...@ho...>
> Cc: <iom...@li...>; 
> <iom...@li...>
> Sent: Monday, October 30, 2006 6:25 PM
> Subject: Re: [Iometer-user] IOMeter Workers under different managers usethe 
> same location for Random read/write.
> 
> 
> > On Mon, 2006-10-30 at 16:00 -0700, Liang Yang wrote:
> >> Hi,
> >>
> >> IOMeter originally plan to use multiple managers for multiple machines 
> >> (each
> >> machine get its own manager). However, I do find some problems when I
> >> spawned multiple managers on the same machine (multiple instances of 
> >> dynamo
> >> are spawned on the same Linux platform).
> >
> > why u want to run multiple dynamo on same box?
> >
> >>
> >> It seems those workers from different managers all use the same position 
> >> for
> >> random read/write, this bring up cache effect even for random read/write
> >> after comparing the data between single manager and multiple managers 
> >> with
> >> the same number of I/Os(cache effect for sequential read/write with 
> >> multiple
> >> workers is obvious as they re-read/re-write the same address).
> >
> > yes, quiet possible.
> >
> >>
> >> I think the same random number icould be broadcasted to all managers 
> >> instead
> >> of broadcasting a unique random number to each manager. This may not be a
> >> good design even though people typically think managers should be on
> >> different machines.
> >
> > it could be changed to start from different seeds.
> >
> >>
> >> Can anyone give me some thoughts here?
> >>
> >> Thanks,
> >>
> >> Liang
> >>
> >>
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> 
> 
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