On Wed, Mar 22, 2017 at 07:39:17PM +0200, Tariq Toukan wrote: > > > > This modification may slow allocations from IRQ context slightly > > > > but the > > > > main gain from the per-cpu allocator is that it scales better for > > > > allocations from multiple contexts. There is an implicit > > > > assumption that > > > > intensive allocations from IRQ contexts on multiple CPUs from a single > > > > NUMA node are rare > Hi Mel, Jesper, and all. > > This assumption contradicts regular multi-stream traffic that is naturally > handled > over close numa cores. I compared iperf TCP multistream (8 streams) > over CX4 (mlx5 driver) with kernels v4.10 (before this series) vs > kernel v4.11-rc1 (with this series). > I disabled the page-cache (recycle) mechanism to stress the page allocator, > and see a drastic degradation in BW, from 47.5 G in v4.10 to 31.4 G in > v4.11-rc1 (34% drop). > I noticed queued_spin_lock_slowpath occupies 62.87% of CPU time.
Can you get the stack trace for the spin lock slowpath to confirm it's from IRQ context? -- Mel Gorman SUSE Labs
