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Subject: Re: [OMPI devel] default btl eager_limit
From: Terry Dontje (Terry.Dontje_at_[hidden])
Date: 2009-07-22 09:27:14


Jeff Squyres wrote:
> Just to follow up for the web archives -- we discussed this on the
> teleconf yesterday and decided that the assert()'s were not the way to
> go. Brian was going to hack up a quick check at the end of OB1
> add_procs that checks each btl's eager_limit, etc. Terry would expand
> this to cover dr and csum.
>
I've received the change from Brian and working on porting it across all
the other PMLs.

--td
>
> On Jul 16, 2009, at 10:10 AM, Terry Dontje wrote:
>
>> Another way to do this which I am not sure makes sense is to just add
>> sizeof(mca_pml_ob1_hdr_t) to the btl_eager_limit passed into by the
>> user. Thus the defining the limit to be specifically for the user data
>> and not the internal headers
>> which the user may not have any inkling about. However, that may lead
>> to the user
>> to not realize there is a man behind the curtain bumping up the limit
>> for the internal headers.
>>
>> --td
>>
>> Terry Dontje wrote:
>> > I was playing around with some really silly fragment sizes (sub 72
>> > bytes) when I ran into some asserts in the btl_openib_sendi. I traced
>> > the assert to be caused by mca_pml_ob1_send_request_start_btl()
>> > calculating the true eager_limit with the following line:
>> >
>> > size_t eager_limit = btl->btl_eager_limit -
>> sizeof(mca_pml_ob1_hdr_t);
>> >
>> > If btl_eager_limit ends up being less than the
>> > sizeof(mca_pml_ob1_hdr_t) the eager_limit calculated results in a very
>> > large number and an assert later on in the stack.
>> >
>> > It seems to me that it would be nice to insert some checks in
>> > mca_btl_base_param_register() to make sure btl_eager_limit is >
>> > sizeof(mca_pml_ob1_hdr_t). Am I missing a reason why this was not
>> > done in the first place?
>> >
>> > --td
>> > _______________________________________________
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>> > devel_at_[hidden]
>> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>
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>
>