[rds-devel] FMR_POOL_SIZE = 1024 for RDS ?

Richard Frank richard.frank at oracle.com
Mon Jan 7 08:22:29 PST 2008


I will with this today

Olaf Kirch wrote:
> On Friday 04 January 2008 22:48, Richard Frank wrote:
>   
>> Is there any reason we would not increase this to 16k or more - what are 
>> the limitations / resource issues here.
>>
>> Allowing only 1024 I/Os outstanding seems low ?
>>     
>
> Okay, I tried 16K, and it doesn't seem to give me any trouble.
> There is some memory overhead here, however - the stack will
> allocate a whole lot of memory in advance. The FMR pool itself
> allocates pool_size * max_pages_per_fmr * sizeof(u64) for the
> page vectors, plus some more memory per FMR. At a pool size of
> 16K and 256 pages per FMR, we're in the vicinity of 30-40Megs
>
> The other limit that may be too low is RDS_FMR_SIZE, which is
> currently at 256. So we're limited to RDMA messages of 1Meg.
> I think we should at least make this a module option. See draft
> patch below.
>
> Olaf
>   



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