Re: slapd memory footprint

[Stelios Grigoriadis <stelios.xx.grigoriadis@ericsson.com>]

Stelios Grigoriadis wrote:
> After running some test we observed that slapd is consuming a 
> considerable amount of memory, why is that? We ran one client that 
> retrieved the entire tree (it was pretty small anyway) and 10 other 
> clients that searched for a particular item. Comparing version 2.3.39 
> with 2.3.32 the footprint increases. From top:
>
> 2.3.32:
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  SWAP CODE 
> DATA COMMAND
> 6049 root      18   0  221m 4904 2568 S 11.5  0.2   0:33.27 216m 2844 
> 137m slapd
>
> 2.3.39:
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  SWAP CODE 
> DATA COMMAND
> 13062 ldap      18   0  268m  80m  77m S 14.3 16.2   0:42.27 188m 2892 
> 185m slapd
>
>
> Is this to be expected? By decreasing the cachesize we got:
>
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  SWAP CODE 
> DATA COMMAND
> 22492 ldap      18   0  255m  80m  77m S 14.5 16.1   0:39.01 175m 2892 
> 172m slapd
>
> which is still pretty big.
>
> The whole ldap tree fits into a 14k large ldif file so the amount of 
> data is notlarge. Is there any way we can influence the memory 
> footprint (eg. by setting som parameter)?
>
> /Stelios

I found out by looking at the code and running som tests that, the 
constants that have
a major impact on the memory footprint are these (are the size of these 
correct?):

BDB_IDL_UM_SIZE, used in search_stack, using approx. 41 % of the memory
SLAP_SLAB_SIZE, used in slap_sl_mem_create, using approx. 5 % of the memory
LDAP_PVT_THREAD_STACK_SIZE, used when creating new threads, using 
approx. 20% of the memory

I couldn't figure out where the rest of the memory usage where, but 
restricting the
max number of threads was the only thing that helped bring the memory 
size down. By
reducing the number of threads to a total of 5 (instead of 14) the 
memory went down
to approx. 130 Mb (which is still a respectable amount).

I've also tried with every possible value of the cache size (didn't 
affect the size much) and idl cache size.

/Stelios