On 2022/6/14 下午10:17, Paul E. McKenney wrote:
On Tue, Jun 14, 2022 at 10:03:35PM +0800, zhangfei.gao@xxxxxxxxxxx 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());
Thank you both for the testing and the proposed fix!
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
And thank you for the testing!
Could you please try fix3 + Neeraj's change of srcu_gp_end?
That is, fix1 + SRCU_MAX_NODELAY_PHASE 1000000 + Neeraj's change of
srcu_gp_end.
Also, at what value of SRCU_MAX_NODELAY_PHASE do the boot
times start rising? This is probably best done by starting with
SRCU_MAX_NODELAY_PHASE=100000 and dividing by (say) ten on each run
until boot time becomes slow, followed by a binary search between the
last two values. (The idea is to bias the search so that fast boot
times are the common case.)
SRCU_MAX_NODELAY_PHASE 100 becomes slower.
8. 5.19-rc1 + fix6: fix4 + SRCU_MAX_NODELAY_PHASE 1000000
real 0m11.154s ~12s
user 0m2.919s
sys 0m1.064s
9. 5.19-rc1 + fix7: fix4 + SRCU_MAX_NODELAY_PHASE 10000
real 0m11.258s
user 0m3.113s
sys 0m1.073s
10. 5.19-rc1 + fix8: fix4 + SRCU_MAX_NODELAY_PHASE 100
real 0m30.053s ~ 32s
user 0m2.827s
sys 0m1.161s
By the way, if build kernel on the board in the meantime (using memory),
time become much longer.
real 1m2.763s
11. 5.19-rc1 + fix9: fix4 + SRCU_MAX_NODELAY_PHASE 1000
real 0m11.443s
user 0m3.022s
sys 0m1.052s
Thanks
More test details: https://docs.qq.com/doc/DRXdKalFPTVlUbFN5
And thank you for these details.
Thanx, Paul
