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SubjectRe: [PATCH net-next 1/3] net: sched: cls_api: add skip_sw counter
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Hi Jamal,

Thank you for the review.

On 2/15/24 17:39, Jamal Hadi Salim wrote:
> +Cc Vlad and Marcelo..
>
> On Thu, Feb 15, 2024 at 11:06 AM Asbjørn Sloth Tønnesen <ast@fiberby.net> wrote:
>>
>> Maintain a count of skip_sw filters.
>>
>> This counter is protected by the cb_lock, and is updated
>> at the same time as offloadcnt.
>>
>> Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
>> ---
>> include/net/sch_generic.h | 1 +
>> net/sched/cls_api.c | 4 ++++
>> 2 files changed, 5 insertions(+)
>>
>> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
>> index 934fdb977551..46a63d1818a0 100644
>> --- a/include/net/sch_generic.h
>> +++ b/include/net/sch_generic.h
>> @@ -476,6 +476,7 @@ struct tcf_block {
>> struct flow_block flow_block;
>> struct list_head owner_list;
>> bool keep_dst;
>> + atomic_t skipswcnt; /* Number of skip_sw filters */
>> atomic_t offloadcnt; /* Number of oddloaded filters */
>
> For your use case is skipswcnt ever going to be any different than offloadcnt?

No, we only use skip_sw filters, since we only use TC as a control path to
install skip_sw rules into hardware.

AFAICT offloadcnt is the sum of skip_sw filters, and filters with no flags which
have implicitly been offloaded.

The reason that I didn't just use offloadcnt, is that I'm not sure if it is
acceptable to treat implicitly offloaded rules without skip_sw, as if they were
explicitly skip_sw. It sounds reasonable, given that the filters without skip_* flags
shouldn't really care.

I tried to only trigger the TC bypass, in the cases that I was absolutely sure would
be safe as a first step.


>
> cheers,
> jamal
>
>> unsigned int nooffloaddevcnt; /* Number of devs unable to do offload */
>> unsigned int lockeddevcnt; /* Number of devs that require rtnl lock. */
>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>> index ca5676b2668e..397c3d29659c 100644
>> --- a/net/sched/cls_api.c
>> +++ b/net/sched/cls_api.c
>> @@ -3483,6 +3483,8 @@ static void tcf_block_offload_inc(struct tcf_block *block, u32 *flags)
>> if (*flags & TCA_CLS_FLAGS_IN_HW)
>> return;
>> *flags |= TCA_CLS_FLAGS_IN_HW;
>> + if (tc_skip_sw(*flags))
>> + atomic_inc(&block->skipswcnt);
>> atomic_inc(&block->offloadcnt);
>> }
>>
>> @@ -3491,6 +3493,8 @@ static void tcf_block_offload_dec(struct tcf_block *block, u32 *flags)
>> if (!(*flags & TCA_CLS_FLAGS_IN_HW))
>> return;
>> *flags &= ~TCA_CLS_FLAGS_IN_HW;
>> + if (tc_skip_sw(*flags))
>> + atomic_dec(&block->skipswcnt);
>> atomic_dec(&block->offloadcnt);
>> }
>>
>> --
>> 2.43.0
>>

--
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby - AS42541

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