[Tarantool-patches] [PATCH vshard 10/11] sched: introduce vshard.storage.sched module
olegrok at tarantool.org
Tue Mar 9 11:03:39 MSK 2021
Hi! Thanks for explanation. LGTM.
On 06.03.2021 01:06, Vladislav Shpilevoy wrote:
> Thanks for the review!
> On 04.03.2021 22:02, Oleg Babin wrote:
>> Hi! I've looked your patch again. See one comment below.
>> On 23.02.2021 03:15, Vladislav Shpilevoy wrote:
>>> +-- Return the remaining timeout in case there was a yield. This helps to save
>>> +-- current clock get in the caller code if there were no yields.
>>> +local function sched_ref_start(timeout)
>>> + local deadline = fiber_clock() + timeout
>>> + local ok, err
>>> + -- Fast-path. Moves are extremely rare. No need to inc-dec the ref queue
>>> + -- then nor try to start some loops.
>>> + if M.move_count == 0 and M.move_queue == 0 then
>>> + goto success
>>> + end
>>> + M.ref_queue = M.ref_queue + 1
>>> + if M.move_count > 0 then
>>> + goto wait_and_retry
>>> + end
>>> + -- Even if move count is zero, must ensure the time usage is fair. Does not
>>> + -- matter in case the moves have no quota at all. That allows to ignore them
>>> + -- infinitely until all refs end voluntarily.
>>> + if M.move_queue > 0 and M.ref_strike >= M.ref_quota and
>>> + M.move_quota > 0 then
>> Is it reasonable to check `move_quota > 0`. According tests it always should be positive.
>> I see similar check for `ref_quota` as well.
> These are special cases covered with tests in unit-tap/scheduler.test.lua
> in test_move_zero_quota() and test_ref_zero_quota().
> Zero quota means the operation can be suppressed by the other operation
> infinitely long.
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