On 10/17/2012 12:13 PM, Eric Dumazet 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 ?) I wouldn't know. I suspect they are running 4GB+ like everyone else. >>> # 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. I agree. Actually, I'm currently doing research for items with smaller memory footprints that this. My current target is devices with 4M RAM and 8M NOR flash. Undoubtedly this is different than what a lot of other people are doing with Linux. > Using SLUB on them might not be the best choice. Indeed. :-) I'm still interested in the dynamics of the slab sizes and how it impacts performance, how much memory is wasted, etc. I think there are a few "power-of-two-and-a-half" kmalloc slabs (e.g. kmalloc-192). Are these configurable anywhere? Anyway, I greatly appreciate the discussion. > 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. I ran a web server on an 8M machine that had an uptime of over 2 years, but that was in the mid-90's. Ahhh - those were the days... -- 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>