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Fix typos in mpmc #2

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Merged
merged 1 commit into from
May 12, 2021
Merged

Fix typos in mpmc #2

merged 1 commit into from
May 12, 2021

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Julian-Chu
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@jserv jserv merged commit 818ad45 into sysprog21:master May 12, 2021
linD026 added a commit to linD026/concurrent-programs that referenced this pull request Apr 22, 2023
@linD026
thread-rcu: Fix incorrect grace period counting
26c01d0 
Currently, the reader_func is counting the number of grace periods based on the value of dut, which is updated by mthpc_rcu_replace_pointer. However, the value of dut actually represents the time we update the value, not the number of grace periods. Also, the original method might result in incorrect counting if someone tried to update the gp_idx while others who saw the same dut value with prev_count still depend on the old gp_idx to increase the counter. To fix the problem, instead of relying on the dut value to increase the gp_idx, we manually increase gp_idx on write side. Then, we can easily determine the gp on read side. For dut value, we simply check the old count value is not greater than the newest one. Additionally, since synchronize_rcu is quite slow, readers generally will pass through the critical section during the first grace period. To generate more realistic output, we add a delay on read side before entering the critical section. Before: 100 reader(s), 5 update run(s), 6 grace period(s) [grace period #0] 100 reader(s) [grace period sysprog21#1] 0 reader(s) [grace period sysprog21#2] 0 reader(s) [grace period sysprog21#3] 0 reader(s) [grace period sysprog21#4] 0 reader(s) [grace period sysprog21#5] 0 reader(s) After, we added a delay: 100 reader(s), 5 update run(s), 6 grace period(s) [grace period #0] 76 reader(s) [grace period sysprog21#1] 0 reader(s) [grace period sysprog21#2] 1 reader(s) [grace period sysprog21#3] 0 reader(s) [grace period sysprog21#4] 3 reader(s) [grace period sysprog21#5] 20 reader(s)
linD026 added a commit to linD026/concurrent-programs that referenced this pull request Apr 22, 2023
@linD026
thread-rcu: Fix incorrect grace period counting
7d16b12 
Currently, the reader_func is counting the number of grace periods based on the value of dut, which is updated by rcu_assign_pointer. However, the value of dut actually represents the time we update the value, not the number of grace periods. Also, the original method might result in incorrect counting if someone tried to update the gp_idx while others who saw the same dut value with prev_count still depend on the old gp_idx to increase the counter. To fix the problem, instead of relying on the dut value to increase the gp_idx, we manually increase gp_idx on write side. Then, we can easily determine the gp on read side. For dut value, we simply check the old count value is not greater than the newest one. Additionally, since synchronize_rcu is quite slow, readers generally will pass through the critical section during the first grace period. To generate more realistic output, we add a delay on read side before entering the critical section. Before: 100 reader(s), 5 update run(s), 6 grace period(s) [grace period #0] 100 reader(s) [grace period sysprog21#1] 0 reader(s) [grace period sysprog21#2] 0 reader(s) [grace period sysprog21#3] 0 reader(s) [grace period sysprog21#4] 0 reader(s) [grace period sysprog21#5] 0 reader(s) After, we added a delay: 100 reader(s), 5 update run(s), 6 grace period(s) [grace period #0] 76 reader(s) [grace period sysprog21#1] 0 reader(s) [grace period sysprog21#2] 1 reader(s) [grace period sysprog21#3] 0 reader(s) [grace period sysprog21#4] 3 reader(s) [grace period sysprog21#5] 20 reader(s)
linD026 added a commit to linD026/concurrent-programs that referenced this pull request Apr 22, 2023
@linD026
thread-rcu: Fix incorrect grace period counting
697f8f8 
Currently, the reader_func is counting the number of grace periods based on the value of dut, which is updated by rcu_assign_pointer. However, the value of dut actually represents the time we update the value, not the number of grace periods. Also, the original method might result in incorrect counting if someone tried to update the gp_idx while others who saw the same dut value with prev_count still depend on the old gp_idx to increase the counter. To fix the problem, instead of relying on the dut value to increase the gp_idx, we manually increase gp_idx on write side. Then, we can easily determine the gp on read side. For dut value, we simply check the old count value is not greater than the newest one. Additionally, since synchronize_rcu is quite slow, readers generally will pass through the critical section during the first grace period. To generate more realistic output, we add a delay on read side before entering the critical section. Before: 100 reader(s), 5 update run(s), 6 grace period(s) [grace period #0] 100 reader(s) [grace period sysprog21#1] 0 reader(s) [grace period sysprog21#2] 0 reader(s) [grace period sysprog21#3] 0 reader(s) [grace period sysprog21#4] 0 reader(s) [grace period sysprog21#5] 0 reader(s) After, we added a delay: 100 reader(s), 5 update run(s), 6 grace period(s) [grace period #0] 76 reader(s) [grace period sysprog21#1] 0 reader(s) [grace period sysprog21#2] 1 reader(s) [grace period sysprog21#3] 0 reader(s) [grace period sysprog21#4] 3 reader(s) [grace period sysprog21#5] 20 reader(s)
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@Julian-Chu @jserv