From: Andrew Rybchenko <arybchenko@solarflare.com>
To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
"stephen@networkplumber.org" <stephen@networkplumber.org>,
"thomas@monjalon.net" <thomas@monjalon.net>,
Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>,
"ferruh.yigit@intel.com" <ferruh.yigit@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, "stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-dev] [EXT] Re: [PATCH] ethdev: fix DMA zone reserve not honoring size
Date: Tue, 2 Apr 2019 11:44:32 +0300 [thread overview]
Message-ID: <a2c0d30a-fdfc-0538-b4e1-bf98272474a4@solarflare.com> (raw)
Message-ID: <20190402084432.nbOtJN9SlIZu25FbA6zZsJ7VMKcWLqO97S88BgsB4yY@z> (raw)
In-Reply-To: <12cbd37b9f47b234459892f8374ac95616070638.camel@marvell.com>
On 4/2/19 11:25 AM, Jerin Jacob Kollanukkaran wrote:
> On Tue, 2019-04-02 at 10:36 +0300, Andrew Rybchenko wrote:
>> On 4/2/19 3:47 AM, Jerin Jacob Kollanukkaran wrote:
>>> On Mon, 2019-04-01 at 10:30 +0300, Andrew Rybchenko wrote:
>>>> External Email
>>>> On 3/31/19 7:25 PM, Pavan Nikhilesh Bhagavatula wrote:
>>>>> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>>>>>
>>>>> The `rte_eth_dma_zone_reserve()` is generally used to create HW
>>>>> rings.
>>>>> In some scenarios when a driver needs to reconfigure the ring
>>>>> size
>>>>> since the named memzone already exists it returns the previous
>>>>> memzone
>>>>> without checking if a different sized ring is requested.
>>>>>
>>>>> Introduce a check to see if the ring size requested is
>>>>> different
>>>>> from the
>>>>> previously created memzone length.
>>>>>
>>>>> Fixes: 719dbebceb81 ("xen: allow determining DOM0 at runtime")
>>>>> Cc: stable@dpdk.org
>>>>>
>>>>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
>>>>> ---
>>>>> lib/librte_ethdev/rte_ethdev.c | 5 ++++-
>>>>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/lib/librte_ethdev/rte_ethdev.c
>>>>> b/lib/librte_ethdev/rte_ethdev.c
>>>>> index 12b66b68c..4ae12e43b 100644
>>>>> --- a/lib/librte_ethdev/rte_ethdev.c
>>>>> +++ b/lib/librte_ethdev/rte_ethdev.c
>>>>> @@ -3604,9 +3604,12 @@ rte_eth_dma_zone_reserve(const struct
>>>>> rte_eth_dev *dev, const char *ring_name,
>>>>> }
>>>>>
>>>>> mz = rte_memzone_lookup(z_name);
>>>>> - if (mz)
>>>>> + if (mz && (mz->len == size))
>>>>> return mz;
>>>>>
>>>>> + if (mz)
>>>>> + rte_memzone_free(mz);
>>>>
>>>> NACK
>>>> I really don't like that API which should reserve does free if
>>>> requested
>>>> size does not match previously allocated.
>>> Why? Is due to API name?
>>
>> 1. The problem really exists. The problem is bad and it very good
>> that you
>> caught it and came up with a patch. Many thanks.
>> 2. Silently free and reallocate memory is bad. Memory could be
>> used/mapped etc.
> If I understand it correctly, Its been used while configuring
> the device and it is per queue, If so, Is there any case where
> memory in use in parallel in real world case with DPDK?
"in real world case with DPDK" is very fragile justification.
I simply don't want to dig in this way since it is very easy to make
a mistake or simply false assumption.
>> 3. As an absolute minimum if we accept the behaviour it must be
>> documented
>> in the function description.
>>
>>> If so,
>>> Can we have rte_eth_dma_zone_reservere_with_resize() then ?
>>> or any another name, You would like to have?
>>
>> 4. I'd prefer an error if different size (or bigger) memzone is
>> requested,
>> but I understand that it can break existing drivers.
>>
>> Thomas, Ferruh, what do you think?
>>
>>>> I understand the motivation, but I don't think the solution is
>>>> correct.
>>> What you think it has correct solution then?
>>
>> See above plus handling in drivers or dedicated function with
>> better name as you suggest above.
> Handling in driver means return error?
Yes.
> Regarding API, Yes, We can add new API. What we will do that exiting
> driver. Is up to driver maintainers to use the new API. I am fine with
> either approach, Just asking the opinion.
You have mine, but I'd like to know what other ethdev maintainers
think about it.
>>> Obviously, We can not allocate max ring size in init time.
>>> If the NIC has support for 64K HW ring, We will be wasting too much
>>> as
>>> it is per queue.
>>
>> Yes, I agree that it is an overkill.
>>
>> net/sfc tries to carefully free/reserve on NIC/queues reconfigure.
>>
>> Many thanks,
>> Andrew.
next prev parent reply other threads:[~2019-04-02 8:44 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-31 16:25 [dpdk-dev] " Pavan Nikhilesh Bhagavatula
2019-03-31 16:25 ` Pavan Nikhilesh Bhagavatula
2019-04-01 7:30 ` Andrew Rybchenko
2019-04-01 7:30 ` Andrew Rybchenko
2019-04-01 9:28 ` Burakov, Anatoly
2019-04-01 9:28 ` Burakov, Anatoly
2019-04-01 9:40 ` Burakov, Anatoly
2019-04-01 9:40 ` Burakov, Anatoly
2019-04-01 12:12 ` [dpdk-dev] [EXT] " Pavan Nikhilesh Bhagavatula
2019-04-01 12:12 ` Pavan Nikhilesh Bhagavatula
2019-04-02 0:47 ` Jerin Jacob Kollanukkaran
2019-04-02 0:47 ` Jerin Jacob Kollanukkaran
2019-04-02 7:36 ` Andrew Rybchenko
2019-04-02 7:36 ` Andrew Rybchenko
2019-04-02 8:25 ` Jerin Jacob Kollanukkaran
2019-04-02 8:25 ` Jerin Jacob Kollanukkaran
2019-04-02 8:44 ` Andrew Rybchenko [this message]
2019-04-02 8:44 ` Andrew Rybchenko
2019-04-04 22:23 ` Thomas Monjalon
2019-04-04 22:23 ` Thomas Monjalon
2019-04-05 8:03 ` Andrew Rybchenko
2019-04-05 8:03 ` Andrew Rybchenko
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