Re: Antw: Re: slapd memory usage

[Howard Chu <hyc@symas.com>]

Ulrich Windl wrote:
>>>> Howard Chu <hyc@symas.com> schrieb am 07.02.2019 um 11:45 in Nachricht
> <07438385-b8a5-92c8-3902-9d3084cbef6d@symas.com>:
>> A. Schulze wrote:
>>>
>>> Howard Chu:
>>>
>>>>> Any idea why the memory usage is so different?
>>>>
>>>> If the only difference is that you set the open file limit to 1024, then it 
>> sounds
>>>> like whatever your default file limit is is much larger.
>>>
>>> Hello Howard,
>>>
>>> yes, it's unlimited by default. Tons of other daemon also run without this 
>> limits here.
>>>
>>> But in contrast: all other daemons don't let explode the memory usage.
>>> Maybe, it worth to find the difference?
>>
>> That *is* the difference. slapd allocates an array of connection info, one 
>> slot per
>> file descriptor. Running with "unlimited" files is clearly a bad idea here.
> 
> OTOH slapd could also allocate the table in chunks of 100 or 1000 descriptors (if ever needed that much)

No. Such strategies invariably lead to failure under heavy load - precisely the time
when you want extra resources to be available for use. Preallocating means we always
have predictable and consistent runtime behavior.

>> In general, running with larger limits than you actually need is a bad idea. 

> Yes, but allocating a huge table that is most likely never needed is also a bad idea IMHO.

It would not be a huge table if you set your resource limits appropriately.

>> This
>> is elementary system administration.

-- 
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/