Re: [RFC][PATCH 1/6] Storing ipcs into IDRs

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Nadia Derbey wrote:

Andi Kleen wrote:


[email protected] writes:



This patch introduces ipcs storage into IDRs. The main changes are:
. This ipc_ids structure is changed: the entries array is changed into a 
   root idr structure.
. The grow_ary() routine is removed: it is not needed anymore when adding 
   an ipc structure, since we are now using the IDR facility.
 . The ipc_rmid() routine interface is changed:
. there is no need for this routine to return the pointer passed in as 
        argument: it is now declared as a void
. since the id is now part of the kern_ipc_perm structure, no need to 
        have it as an argument to the routine




Thanks for doing this work. It was long overdue.
Do you have any data how this changes memory consumption with many objects? 
-Andi



Andi,
Here are the results I got when creating 32768 (IPCMNI) msg queues with the patched kernel: 

http://akt.sourceforge.net/results/2.6.23-rc2-idr/msg11/output.new

It's the output from msg11.c. This script does what follows:
    . gets sysinfo(2) results
    . captures /proc/meminfo
    . captures /proc/slabinfo
    . creates XX msg queues (XX given as parameter)
    . captures /proc/meminfo
    . captures /proc/slabinfo
    . gets sysinfo results
    . outputs all the results
    . removes the created ipcs

sysinfo results: a BEFORE and an AFTER column are output where necessary.
BEFORE means "before creating the objects"
AFTER means "after the objects have been created"

meminfo results: the BEFORE and AFTER files are pasted
slabinfo results: only the differences between the BEFORE and the AFTER are output. 


Here are also the sizes for the ref and the patched kernel:

size linux-2.6.23-rc2.ref/vmlinux linux-2.6.23-rc2/vmlinux
   text    data     bss     dec     hex filename
4432697  496450  602112 5531259  54667b linux-2.6.23-rc2.ref/vmlinux
4430747  496450  602112 5529309  545edd linux-2.6.23-rc2/vmlinux
The http://akt.sourceforge.net/results/2.6.23-rc2-idr/msg11 directory is structured as follows: 

msg11.c: the script I used to generate the results
output.ref: the output from msg11 with the ref kernel
output.new: the output from msg11 with the patched kernel
size: the output from the size command
ref: directory with the results files for the ref kernel
new: directory with the results files for the patched kernel
In these 2 directories:
*_mem_*before: /proc/meminfo before creating the msg queues
*_mem_*after: /proc/meminfo after creating the msg queues
*_slab_*before: /proc/slabinfo before creating the msg queues
*_slab_*after: /proc/slabinfo after creating the msg queues



Andi,
Here is an annalysis of the results I sent you yesterday (I guess you don't have enoguh time to look at everything): 

ref code:
1) since /proc/sys/kernel/msgmni has been set to 32768, vmalloc(0x20014) is called to allocate the entries[] array (see grow_ary() --> ipc_rcu_alloc()). 

==>

Before msg queues allocation:  VmallocUsed = 2860 kB
After msg queues allocation:   VmallocUsed = 2996 KB

Once allocated this array is never freed.
Unfortunately, in the result I sent you yesterday, you can't see the evolution since it was not the 1st time I was running the test, so the vmalloc() has not been called. 


2) Since 32768 msg queues have been created and a msg_queue structure <
PAGE_SIZE, kmalloc(0x6C) is called 32768 times
==> size-128 in slabinfo: (I slighty simplified the output to make it fit in the mail): 

                              objs          slabs
         # name   <active>  <num> <size> : <active> <num>
before : size-128     1070   1320    128 :       44    44
after  : size-128    33840  33840    128 :     1128  1128


patched code:
1) since 32768 msg queues are created, idr_pre_get() is called 32768 times
==> idr_layer_cache in slabinfo:

                                        objs          slabs
         # name           <active>  <num> <size> : <active> <num>
before : idr_layer_cache       112    116    136 :        4     4
after  : idr_layer_cache      1189   1189    136 :       41    41

2) This point remains unchanged compared to the ref code.



Regards,
Nadia
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