Ray Fucillo wrote:
> Nick Piggin wrote:
> 
>> fork() can be changed so as not to set up page tables for
>> MAP_SHARED mappings. I think that has other tradeoffs like
>> initially causing several unavoidable faults reading
>> libraries and program text.
>>
>> What kind of application are you using?
> 
> 
> The application is a database system called Caché.  We allocate a large 
> shared memory segment for database cache, which in a large production 
> environment may realistically be 1+GB on 32-bit platforms and much 
> larger on 64-bit.  At these sizes fork() is taking hundreds of 
> miliseconds, which can become a noticeable bottleneck for us.  This 
> performance characteristic seems to be unique to Linux vs other Unix 
> implementations.
> 
> 

As Andi said, hugepages might be a very nice feature for you guys
to look into and might potentially give a performance increase with
reduced TLB pressure, not only your immediate fork problem.

Anyway, the attached patch is something you could try testing. If
you do so, then I would be very interested to see performance results.

Thanks,
Nick

-- 
SUSE Labs, Novell Inc.