On Mon, Dec 09, 2013 at 12:11:33PM +0530, Aneesh Kumar K.V wrote: > Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes: > > > Subject: sched: Revert need_resched() to look at TIF_NEED_RESCHED > > From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Date: Fri Sep 27 17:20:30 CEST 2013 > > > > Yuanhan reported a serious throughput regression in his pigz > > benchmark. Using the ftrace patch I found that several idle paths > > need more TLC before we can switch the generic need_resched() over to > > preempt_need_resched. > > > > The preemption paths benefit most from preempt_need_resched and do > > indeed use it; all other need_resched() users don't really care that > > much so reverting need_resched() back to tif_need_resched() is the > > simple and safe solution. > > > > Reported-by: Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx> > > Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > I guess we still need to fix should_resched() I am hitting the below > with upstream > > > BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-ppc:4394] > Modules linked in: > CPU: 0 PID: 4394 Comm: qemu-system-ppc Not tainted 3.13.0-rc3+ #98 > task: c0000001d0788400 ti: c0000001dca00000 task.ti: c0000001dca00000 > NIP: c00000000082dd80 LR: c000000000081ae0 CTR: c000000000062ba0 > REGS: c0000001dca02f70 TRAP: 0901 Not tainted (3.13.0-rc3+) > MSR: 8000000000009032 <SF,EE,ME,IR,DR,RI> CR: 24822024 XER: 00000000 > CFAR: c000000000081adc SOFTE: 1 > GPR00: c000000000081ae0 c0000001dca031f0 c000000000d67ab0 0000000000000001 > GPR04: 0000000071000002 0000000000000001 00000189a0d786b7 00000000018c0000 > GPR08: 0000000000000001 0000000000000000 0000000000000000 c000000000da0000 > GPR12: 0000000000000c00 c00000000fef0000 > NIP [c00000000082dd80] ._cond_resched+0x0/0x40 > LR [c000000000081ae0] .kvmppc_prepare_to_enter+0x2a0/0x2e0 > Call Trace: > [c0000001dca031f0] [c000000000081ae0] .kvmppc_prepare_to_enter+0x2a0/0x2e0 (unreliable) > [c0000001dca03290] [c00000000008f2cc] .kvmppc_handle_exit_pr+0xec/0xa40 > [c0000001dca03340] [c0000000000918c4] kvm_start_lightweight+0xac/0xbc > [c0000001dca03510] [c00000000008efe0] .kvmppc_vcpu_run_pr+0x130/0x2a0 > [c0000001dca039e0] [c0000000000855bc] .kvmppc_vcpu_run+0x2c/0x40 > [c0000001dca03a50] [c000000000082c94] .kvm_arch_vcpu_ioctl_run+0x54/0x1b0 > [c0000001dca03ae0] [c00000000007d5f8] .kvm_vcpu_ioctl+0x478/0x740 > [c0000001dca03ca0] [c000000000218864] .do_vfs_ioctl+0x4a4/0x760 > [c0000001dca03d80] [c000000000218b78] .SyS_ioctl+0x58/0xb0 > [c0000001dca03e30] [c000000000009e58] syscall_exit+0x0/0x98 > Instruction dump: > e92d0260 e94911c0 812a0004 5529f07e 5529103e 912a0004 38210080 e8010010 > ebc1fff0 ebe1fff8 7c0803a6 4e800020 <7c0802a6> 38600000 f8010010 f821ff91 > > > The revert which Alexander tried had those > > http://mid.gmane.org/20131128132641.GP10022@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -ENOPARSE.. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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