On Wed, 2013-06-19 at 12:11 +0300, Michael S. Tsirkin wrote: > Well KVM supports up to 160 VCPUs on x86. > > Creating a queue per CPU is very reasonable, and > assuming cache line size of 64 bytes, netdev_queue seems to be 320 > bytes, that's 320*160 = 51200. So 12.5 pages, order-4 allocation. > I agree most people don't have such systems yet, but > they do exist.
Even so, it will just work, like a fork() is likely to work, even if a process needs order-1 allocation for kernel stack. Some drivers still use order-10 allocations with kmalloc(), and nobody complained yet. We had complains with mlx4 driver lately only bcause kmalloc() now gives a warning if allocations above MAX_ORDER are attempted. Having a single pointer means that we can : - Attempts a regular kmalloc() call, it will work most of the time. - fallback to vmalloc() _if_ kmalloc() failed. Frankly, if you want one tx queue per cpu, I would rather use NETIF_F_LLTX, like some other virtual devices. This way, you can have real per cpu memory, with proper NUMA affinity. -- 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/
