Messages in this thread | | | Subject | Re: Commit 282d8998e997 (srcu: Prevent expedited GPs and blocking readers from consuming CPU) cause qemu boot slow | From | "" <> | Date | Tue, 14 Jun 2022 22:57:04 +0800 |
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On 2022/6/14 下午10:14, Neeraj Upadhyay wrote: > > > On 6/14/2022 7:33 PM, zhangfei.gao@foxmail.com wrote: >> >> >> On 2022/6/14 下午8:19, Neeraj Upadhyay wrote: >>> >>>> >>>> 5.18-rc4 based ~8sec >>>> >>>> 5.19-rc1 ~2m43sec >>>> >>>> 5.19-rc1+fix1 ~19sec >>>> >>>> 5.19-rc1-fix2 ~19sec >>>> >>> >>> If you try below diff on top of either 5.19-rc1+fix1 or >>> 5.19-rc1-fix2 ; does it show any difference in boot time? >>> >>> --- a/kernel/rcu/srcutree.c >>> +++ b/kernel/rcu/srcutree.c >>> @@ -706,7 +706,7 @@ static void srcu_schedule_cbs_snp(struct >>> srcu_struct *ssp, struct srcu_node *snp >>> */ >>> static void srcu_gp_end(struct srcu_struct *ssp) >>> { >>> - unsigned long cbdelay; >>> + unsigned long cbdelay = 1; >>> bool cbs; >>> bool last_lvl; >>> int cpu; >>> @@ -726,7 +726,9 @@ static void srcu_gp_end(struct srcu_struct *ssp) >>> spin_lock_irq_rcu_node(ssp); >>> idx = rcu_seq_state(ssp->srcu_gp_seq); >>> WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); >>> - cbdelay = !!srcu_get_delay(ssp); >>> + if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), >>> READ_ONCE(ssp->srcu_gp_seq_needed_exp))) >>> + cbdelay = 0; >>> + >>> WRITE_ONCE(ssp->srcu_last_gp_end, ktime_get_mono_fast_ns()); >>> >> Test here: >> qemu: https://github.com/qemu/qemu/tree/stable-6.1 >> kernel: >> https://github.com/Linaro/linux-kernel-uadk/tree/uacce-devel-5.19-srcu-test >> (in case test patch not clear, push in git tree) >> >> Hardware: aarch64 >> >> 1. 5.18-rc6 >> real 0m8.402s >> user 0m3.015s >> sys 0m1.102s >> >> 2. 5.19-rc1 >> real 2m41.433s >> user 0m3.097s >> sys 0m1.177s >> >> 3. 5.19-rc1 + fix1 from Paul >> real 2m43.404s >> user 0m2.880s >> sys 0m1.214s >> >> 4. 5.19-rc1 + fix2: fix1 + Remove "if (!jbase)" block >> real 0m15.262s >> user 0m3.003s >> sys 0m1.033s >> >> When build kernel in the meantime, load time become longer. >> >> 5. 5.19-rc1 + fix3: fix1 + SRCU_MAX_NODELAY_PHASE 1000000 >> real 0m15.215s >> user 0m2.942s >> sys 0m1.172s >> >> 6. 5.19-rc1 + fix4: fix1 + Neeraj's change of srcu_gp_end >> real 1m23.936s >> user 0m2.969s >> sys 0m1.181s >> > 7. 5.19-rc1 + fix5: fix4 + Remove "if (!jbase)" block
real 0m11.418s
user 0m3.031s
sys 0m1.067s
8. 5.19-rc1 + fix 6: fix4 + SRCU_MAX_NODELAY_PHASE 1000000
real 0m11.154s ~12s
user 0m2.919s
sys 0m1.064s
Thanks
> Thanks for this data. Can you please share below test combo also? > > 7. 5.19-rc1 + fix5: fix2 + Neeraj's change of srcu_gp_end > > > 8. 5.19-rc1 + fix6: fix3 + Neeraj's change of srcu_gp_end > > > Thanks > Neeraj > >> More test details: https://docs.qq.com/doc/DRXdKalFPTVlUbFN5 >> >> Thanks >>
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