On Tue, 2012-10-16 at 15:27 -0300, Ezequiel Garcia wrote:
> Yes, we have some numbers:
>
> http://elinux.org/Kernel_dynamic_memory_analysis#Kmalloc_objects
>
> Are they too informal? I can add some details...
>
> They've been measured on a **very** minimal setup, almost every option
> is stripped out, except from initramfs, sysfs, and trace.
>
> On this scenario, strings allocated for file names and directories
> created by sysfs
> are quite noticeable, being 4-16 bytes, and produce a lot of fragmentation
> from
> that 32 byte cache at SLAB.
>
> Is an option to enable small caches on SLUB and SLAB worth it?
Random small web server :
# free
total used free shared buffers cached
Mem: 7884536 5412572 2471964 0 155440 1803340
-/+ buffers/cache: 3453792 4430744
Swap: 2438140 51164 2386976
# grep Slab /proc/meminfo
Slab: 351592 kB
# egrep "kmalloc-32|kmalloc-16|kmalloc-8" /proc/slabinfo
kmalloc-32 11332 12544 32 128 1 : tunables 0 0 0 :
slabdata 98 98 0
kmalloc-16 5888 5888 16 256 1 : tunables 0 0 0 :
slabdata 23 23 0
kmalloc-8 76563 82432 8 512 1 : tunables 0 0 0 :
slabdata 161 161 0
Really, some waste on these small objects is pure noise on SMP hosts.
(Waste on bigger objects is probably more important by orders of magnitude)
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