[Gluster-devel] What do extra_free and extrastd_free params do in the dictionary object?

[Xavi Hernandez]

On Thu, Jan 9, 2020 at 9:44 AM Amar Tumballi <amarts at gmail.com> wrote:

>
>
> On Thu, Jan 9, 2020 at 1:38 PM Xavi Hernandez <jahernan at redhat.com> wrote:
>
>> On Sun, Dec 22, 2019 at 4:56 PM Yaniv Kaul <ykaul at redhat.com> wrote:
>>
>>> I could not find a relevant use for them. Can anyone enlighten me?
>>>
>>
>> I'm not sure why they are needed. They seem to be used to keep the
>> unserialized version of a dict around until the dict is destroyed. I
>> thought this could be because we were using pointers to the unserialized
>> data inside dict, but that's not the case currently. However, checking very
>> old versions (pre 3.2), I see that dict values were not allocated, but a
>> pointer to the unserialized data was used.
>>
>
> Xavi,
>
> While you are right about the intent, it is used still, at least when I
> grepped latest repo to keep a reference in protocol layer.
>
> This is done to reduce a copy after the dictionary's binary content is
> received from RPC. The 'extra_free' flag is used when we use a
> GF_*ALLOC()'d buffer in protocol to receive dictionary, and extra_stdfree
> is used when RPC itself allocates the buffer and hence uses 'free()' to
> free the buffer.
>

I don't see it. When dict_unserialize() is called, key and value are
allocated and copied, so  why do we need to keep the raw data after that ?

In 3.1 the value was simply a pointer to the unserialized data, but
starting with 3.2, value is memdup'ed. Key is always copied. I don't see
any other reference to the unserialized data right now. I think that
instead of assigning the raw data to extra_(std)free, we should simply
release that memory and remove those fields.

Am I missing something else ?


>
>> I think this is not needed anymore. Probably we could remove these fields
>> if that's the only reason.
>>
>
> If keeping them is hard to maintain, we can add few allocation to remove
> those elements, that shouldn't matter much IMO too. We are not using
> dictionary itself as protocol now (which we did in 1.x series though).
>
> Regards,
> Amar
> ---
> https://kadalu.io
>
>
>
>> TIA,
>>> Y.
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