On Fri, Feb 22, 2019 at 12:45:44PM +0000, Mel Gorman wrote: > On Mon, Feb 18, 2019 at 09:49:10AM -0800, Linus Torvalds wrote: > > On Mon, Feb 18, 2019 at 9:40 AM Peter Zijlstra <pet...@infradead.org> wrote: > > > > > > However; whichever way around you turn this cookie; it is expensive and > > > nasty. > > > > Do you (or anybody else) have numbers for real loads? > > > > Because performance is all that matters. If performance is bad, then > > it's pointless, since just turning off SMT is the answer. > > > > I tried to do a comparison between tip/master, ht disabled and this series > putting test workloads into a tagged cgroup but unfortunately it failed > > [ 156.978682] BUG: unable to handle kernel NULL pointer dereference at > 0000000000000058 > [ 156.986597] #PF error: [normal kernel read fault] > [ 156.991343] PGD 0 P4D 0
When bodged around, one test survived (performance was crucified but the benchmark is very synthetic). pgbench (test 2) paniced with a hard lockup. Most of the console log was corrupted (unrelated to the patch) but the relevant part is [ 4587.419674] Call Trace: [ 4587.419674] _raw_spin_lock+0x1b/0x20 [ 4587.419675] sched_core_balance+0x155/0x520 [ 4587.419675] ? __switch_to_asm+0x34/0x70 [ 4587.419675] __balance_callback+0x49/0xa0 [ 4587.419676] __schedule+0xf15/0x12c0 [ 4587.419676] schedule_idle+0x1e/0x40 [ 4587.419677] do_idle+0x166/0x280 [ 4587.419677] cpu_startup_entry+0x19/0x20 [ 4587.419678] start_secondary+0x17a/0x1d0 [ 4587.419678] secondary_startup_64+0xa4/0xb0 [ 4587.419679] Kernel panic - not syncing: Hard LOCKUP -- Mel Gorman SUSE Labs
