Re: [Tarantool-patches] [PATCH v2] lua: remove excess Lua call from table encoding

[Sergey Kaplun <skaplun@tarantool.org>]

Hi! Thanks for your comment!

@Changelog:
 * Refactor Lua table encoding: removed excess Lua function object and
left protected Lua frame only for the case __serialize is a function
to improve `msgpack.encode()` performance.

On 08.06.20, Sergey Ostanevich wrote:
> Hi!
> 
> The patch looks ok after I figured out that you actually sink the pcall
> down the callstack, keeping it only for the case __serialize is a
> function, leaving all other cases as is.
> 
> What misled me is the changelog, where you mentioned you _removed_
> protected frame:
> 
>   * Refactor Lua table encoding: removed excess Lua function object and
>   protected Lua frame creation to improve `msgpack.encode()` performance.
> 
> I believe it'll be better to update the changelog descripton.
> 
> 
> LGTM,
> 
> Sergos
> 
> 
> On 05 июн 10:14, Sergey Kaplun wrote:
> > Hi!
> > 
> > It's a little bit complicated to find a good test that shows the
> > difference of behaviour. AFAIK there is only one case when we can face
> > with OOM error or so on - reallocating of Lua stack. But it can happen
> > with old version too (when we push cfunction, table or lightuserdata at
> > Lua stack before pcall). Now instead three values we push at Lua stack
> > only two (Lua function from metatable and table itself if serializing
> > function exists) before pcall. So with this patch the probability of
> > raising OOM error should be decreased.
> > 
> > Of course we can check it with an eror injection, but it can be catched
> > with old behaviour too. It will be nice if you can provide any idea of
> > this kind of test to check this.
> > 
> > On 02.06.20, Sergey Ostanevich wrote:
> > > Hi!
> > > 
> > > Thanks for the patch!
> > > 
> > > Still I would like to see some tests - perhaps with errinj to emulate
> > > OOM or some other case that trigger the 'excess protected frame' need.
> > > So that after your changes it still passes.
> > > 
> > > Regards,
> > > Sergos
> > > 
> > 
> > -- 
> > Best regards,
> > Sergey Kaplun

-- 
Best regards,
Sergey Kaplun