Messages in this thread | | | Date | Wed, 18 May 2022 17:55:11 +0800 | Subject | Re: [PATCH 1/2] psi: add support for multi level pressure stall trigger | From | Chen Wandun <> |
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在 2022/5/18 1:35, Suren Baghdasaryan 写道: > On Tue, May 17, 2022 at 5:46 AM Chen Wandun <chenwandun@huawei.com> wrote: >> >> >> 在 2022/5/16 16:43, Suren Baghdasaryan 写道: >>> On Mon, May 16, 2022 at 1:21 AM Suren Baghdasaryan <surenb@google.com> wrote: >>>> On Sun, May 15, 2022 at 11:20 PM Alex Shi <seakeel@gmail.com> wrote: >>>>> >>>>> On 5/16/22 11:35, Chen Wandun wrote: >>>>>> Nowadays, psi events are triggered when stall time exceed >>>>>> stall threshold, but no any different between these events. >>>>>> >>>>>> Actually, events can be divide into multi level, each level >>>>>> represent a different stall pressure, that is help to identify >>>>>> pressure information more accurately. >>>> IIUC by defining min and max, you want the trigger to activate when >>>> the stall is between min and max thresholds. But I don't see why you >>>> would need that. If you want to have several levels, you can create >>>> multiple triggers and monitor them separately. For your example, that >>>> would be: >>>> >>>> echo "some 150000 1000000" > /proc/pressure/memory >>>> echo "some 350000 1000000" > /proc/pressure/memory >>>> >>>> Your first trigger will fire whenever the stall exceeds 150ms within >>>> each 1sec and the second one will trigger when it exceeds 350ms. It is >>>> true that if the stall jumps sharply above 350ms, you would get both >>>> triggers firing. I'm guessing that's why you want this functionality >>>> so that 150ms trigger does not fire when 350ms one is firing but why >>>> is that a problem? Can't userspace pick the highest level one and >>>> ignore all the lower ones when this happens? Or are you addressing >>>> some other requirement? >>>> >>>>>> echo "some 150000 350000 1000000" > /proc/pressure/memory would >>>>> This breaks the old ABI. And why you need this new function? >>>> Both great points. >>> BTW, I think the additional max_threshold parameter could be >>> implemented in a backward compatible way so that the old API is not >>> broken: >>> >>> arg_count = sscanf(buf, "some %u %u %u", &min_threshold_us, &arg2, &arg3); >>> if (arg_count < 2) return ERR_PTR(-EINVAL); >>> if (arg_count < 3) { >>> max_threshold_us = INT_MAX; >>> window_us = arg2; >>> } else { >>> max_threshold_us = arg2; >>> window_us = arg3; >>> } >> OK >> >> Thanks. >>> But again, the motivation still needs to be explained. >> we want do different operation for different stall level, >> just as prev email explain, multi trigger is also OK in old >> ways, but it is a litter complex. > Ok, so the issue can be dealt with in the userspace but would make it > simpler if max_threashold is supported by the kernel. I can buy this > argument if the kernel implementation is not complex and max_threshold > is added in a way that does not break current users. I believe both > conditions can be met. OK, I will send v2
Thanks > >>>>> Thanks >>>>> >>>>>> add [150ms, 350ms) threshold for partial memory stall measured >>>>>> within 1sec time window. >>>>>> >>>>>> Signed-off-by: Chen Wandun <chenwandun@huawei.com> >>>>>> --- >>>>>> include/linux/psi_types.h | 3 ++- >>>>>> kernel/sched/psi.c | 19 +++++++++++++------ >>>>>> 2 files changed, 15 insertions(+), 7 deletions(-) >>>>>> >>>>>> diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h >>>>>> index c7fe7c089718..2b1393c8bf90 100644 >>>>>> --- a/include/linux/psi_types.h >>>>>> +++ b/include/linux/psi_types.h >>>>>> @@ -119,7 +119,8 @@ struct psi_trigger { >>>>>> enum psi_states state; >>>>>> >>>>>> /* User-spacified threshold in ns */ >>>>>> - u64 threshold; >>>>>> + u64 min_threshold; >>>>>> + u64 max_threshold; >>>>>> >>>>>> /* List node inside triggers list */ >>>>>> struct list_head node; >>>>>> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c >>>>>> index 6f9533c95b0a..17dd233b533a 100644 >>>>>> --- a/kernel/sched/psi.c >>>>>> +++ b/kernel/sched/psi.c >>>>>> @@ -541,7 +541,7 @@ static u64 update_triggers(struct psi_group *group, u64 now) >>>>>> >>>>>> /* Calculate growth since last update */ >>>>>> growth = window_update(&t->win, now, total[t->state]); >>>>>> - if (growth < t->threshold) >>>>>> + if (growth < t->min_threshold || growth >= t->max_threshold) >>>>>> continue; >>>>>> >>>>>> t->pending_event = true; >>>>>> @@ -1087,15 +1087,18 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, >>>>>> { >>>>>> struct psi_trigger *t; >>>>>> enum psi_states state; >>>>>> - u32 threshold_us; >>>>>> + u32 min_threshold_us; >>>>>> + u32 max_threshold_us; >>>>>> u32 window_us; >>>>>> >>>>>> if (static_branch_likely(&psi_disabled)) >>>>>> return ERR_PTR(-EOPNOTSUPP); >>>>>> >>>>>> - if (sscanf(buf, "some %u %u", &threshold_us, &window_us) == 2) >>>>>> + if (sscanf(buf, "some %u %u %u", &min_threshold_us, >>>>>> + &max_threshold_us, &window_us) == 3) >>>>>> state = PSI_IO_SOME + res * 2; >>>>>> - else if (sscanf(buf, "full %u %u", &threshold_us, &window_us) == 2) >>>>>> + else if (sscanf(buf, "full %u %u %u", &min_threshold_us, >>>>>> + &max_threshold_us, &window_us) == 3) >>>>>> state = PSI_IO_FULL + res * 2; >>>>>> else >>>>>> return ERR_PTR(-EINVAL); >>>>>> @@ -1107,8 +1110,11 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, >>>>>> window_us > WINDOW_MAX_US) >>>>>> return ERR_PTR(-EINVAL); >>>>>> >>>>>> + if (min_threshold_us >= max_threshold_us) >>>>>> + return ERR_PTR(-EINVAL); >>>>>> + >>>>>> /* Check threshold */ >>>>>> - if (threshold_us == 0 || threshold_us > window_us) >>>>>> + if (max_threshold_us > window_us) >>>>>> return ERR_PTR(-EINVAL); >>>>>> >>>>>> t = kmalloc(sizeof(*t), GFP_KERNEL); >>>>>> @@ -1117,7 +1123,8 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, >>>>>> >>>>>> t->group = group; >>>>>> t->state = state; >>>>>> - t->threshold = threshold_us * NSEC_PER_USEC; >>>>>> + t->min_threshold = min_threshold_us * NSEC_PER_USEC; >>>>>> + t->max_threshold = max_threshold_us * NSEC_PER_USEC; >>>>>> t->win.size = window_us * NSEC_PER_USEC; >>>>>> window_reset(&t->win, 0, 0, 0); >>>>>> >>> . > .
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