On Wed, Oct 17, 2012 at 12:13 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Wed, 2012-10-17 at 11:45 -0700, Tim Bird wrote: > >> 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... :-) >> > > Even laptops in 2012 have +4GB of ram. > > (Maybe not Sony laptops, I have to double check ?) > > Yes, servers do have more ram than laptops. > > (Maybe not Sony servers, I have to double check ?) > >> > # 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. > > > I said : > > <quote> > I would remove small kmalloc-XX caches, as sharing a cache line > is sometime dangerous for performance, because of false sharing. > > They make sense only for very small hosts > </quote> > > I think your 10M cameras are very tiny hosts. > > Using SLUB on them might not be the best choice. > > First time I ran linux, years ago, it was on 486SX machines with 8M of > memory (or maybe less, I dont remember exactly). But I no longer use > this class of machines with recent kernels. > > # size vmlinux > text data bss dec hex filename > 10290631 1278976 1896448 13466055 cd79c7 vmlinux > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
Potentially stupid question But is SLAB the one where all objects per cache have a fixed size and thus you don't have any bookkeeping overhead for the actual allocations? I remember something about one of the allocation mechanisms being designed for caches of fixed sized objects to minimize the need for bookkeeping. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
