On 10/16/2012 12:16 PM, Eric Dumazet wrote: > 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 8G is a small web server? The RAM budget for Linux on one of Sony's cameras was 10M. We're not merely not in the same ballpark - you're in a ballpark and I'm trimming bonsai trees... :-) > # 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. In this example, it appears that if all kmalloc-8's were pushed into 32-byte slabs, we'd lose about 1.8 meg due to pure slab overhead. This would not be noise on my system. > (Waste on bigger objects is probably more important by orders of magnitude) Maybe. I need to run some measurements on systems that are more similar to what we're deploying in products. I'll see if I can share them. -- Tim ============================= Tim Bird Architecture Group Chair, CE Workgroup of the Linux Foundation Senior Staff Engineer, Sony Network Entertainment ============================= -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>