Savage Attacker feat with multiple damage dice

lets be quick....

this dice may not be allowed by rule but bear with me, this is just case scenario to clear the confusion 

flame tongue greatsword + booming blade + holy weapon + sneak attack

let say the dice are like this

(2d6+2d6) + 1d8 + 2d8 + 3d6

how the savage attacker feat interact with this dice, which dice are affected and which dice that are dont (eg:hex, hunters mark, or any other extra dice damage)

Per Sage Advice here, only "the weapon's damage dice" are affected by Savage Attacker.

That answer is, of course, not super helpful in determining what actually counts as "the weapon's damage dice". However, it seems pretty clear that add-on effects like Sneak Attack, Hex, Holy Weapon etc. are not intended to count. (You couldn't use Sneak Attack with a greatsword anyway, but whatever.)

So the magic weapon, the extra damage from flame tongue can't benefits from savage attacker?

The relevant part of the feat is:

you can roll the weapon’s damage dice twice

Only the damage dice that belong to the weapon get affected, not other dice added to the attack by another ability.

In the case you're presenting, both the base dice and the flame tongue dice are inherent to the weapon, so you can roll only those twice.

So the extra dice from magic weapon can benefits from savage attacker then...

As per holy weapon description 

"weapon attacks made with it deal an extra 2d8 radiant damage on a hit. If the weapon isn’t already a magic weapon, it becomes one"

For non magical weapon The weapon become magical and it deals an extra 2d8, can those dice also benefits from savage attacker?

Quote from LowLevel_NPC >>

So the extra dice from magic weapon can benefits from savage attacker then...

And per holy weapon description 

"weapon attacks made with it deal an extra 2d8 radiant damage on a hit. If the weapon isn’t already a magic weapon, it becomes one"

The weapon become magical and it deals an extra 2d8, can those dice also benefits from savage attacker?

No. As I said, Sage Advice makes it pretty clear that add-on effects from spells like Holy Weapon are not intended to be affected by Savage Attacker. Only the weapon's own damage dice are affected.

That said, Savage Attacker is a pretty weak feat if you don't have something like a Flame Tongue Greatsword that rolls a lot of damage dice, so in practice some DMs might allow other effects to count.

I'm still confused 

Flame tongue 

"While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits."

Both had similar wording.

The holy weapon turn weapon into magical, so both is magic weapon

Yet they treated differently...

Quote from wagnarokkr >>

Quote from LowLevel_NPC >>

So the extra dice from magic weapon can benefits from savage attacker then...

And per holy weapon description 

"weapon attacks made with it deal an extra 2d8 radiant damage on a hit. If the weapon isn’t already a magic weapon, it becomes one"

The weapon become magical and it deals an extra 2d8, can those dice also benefits from savage attacker?

No. As I said, Sage Advice makes it pretty clear that add-on effects from spells like Holy Weapon are not intended to be affected by Savage Attacker. Only the weapon's own damage dice are affected.

 Yeah. The attack gains the dice, not the weapon itself. 

If a boring character with no abilities, no equipment, and no spells or the like affecting them could roll the dice when using the weapon, then the dice are candidates for savage attacker.

Quote from LowLevel_NPC >>

I'm still confused 

Flame tongue 

"While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits."

Both had similar wording.

The holy weapon turn weapon into magical, so both is magic weapon

Yet they treated differently...

Flame Tongue's extra damage dice are part of the weapon's damage dice. Holy Weapon is an external effect, not an innate part of the weapon. That's the difference, not the specific wording. Whether the effect is magical doesn't matter.

Quote from wagnarokkr >>

Flame Tongue's extra damage dice are part of the weapon's damage dice. Holy Weapon is an external effect, not an innate part of the weapon. That's the difference, not the specific wording. Whether the effect is magical doesn't matter.

 The wording is different, as well.

"While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits."

vs 

weapon attacks made with it deal an extra 2d8 radiant damage on a hit.

The attack deals extra dice of damage, not the weapon itself.

Nonetheless, "is this part of the weapon, or an external ability" is probably an easier guideline to work with. It's both easier to figure out, and it doesn't require the writers to have got the wording precisely correct, which is not a guarantee for official books, much less third-party.

To put it simply, the weapon's damage dice = dice in weapon's Damage column

Damage. The table lists the amount of damage a weapon deals when an attacker hits with it as well as the type of that damage.

Quote from Plaguescarred >>

To put it simply, the weapon's damage dice = dice in weapon's Damage column

Damage. The table lists the amount of damage a weapon deals when an attacker hits with it as well as the type of that damage.

I don't think it's that simple, as if you follow that strictly, you're not including the extra damage dice of a magic weapon like a Flame Tongue. Perhaps it'd be better to say that only damage dice included in the weapon's description are affected.

Possible i'd handle it case by case but i think it's fair to think the feat assume this at base. 

With only the knowledge in this thread.

an extra 2d6 fire damage

Would the fact this is "extra" mean it is not a part of the weapon?

Quote from Character77006 >>

With only the knowledge in this thread.

an extra 2d6 fire damage

Would the fact this is "extra" mean it is not a part of the weapon?

No. Again, the fact that it is part of the description of the weapon means it's part of the weapon.

Quote from Character77006 >>

With only the knowledge in this thread.

an extra 2d6 fire damage

Would the fact this is "extra" mean it is not a part of the weapon?

The key is:

While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits.

"It" refers to the weapon. So the weapon is dealing the "extra" 2d6 fire damage. Not the attack. Not even "weapon attacks", which only specify that a weapon must be used, not where the extra damage actually comes from.

Quote from LowLevel_NPC >>

So the magic weapon, the extra damage from flame tongue can't benefits from savage attacker?

 If it's useful for you, I shared in Savage Attacker, Great Weapon Fighting and extra damage dice this conversation with the Dev (link to sageadvice.eu) mentioning Flame Tongue and Frost Brand:

@Il_Gama Great Weapon Fighting and Battlemaster' Sweeping Attack: may I reroll the 1 and 2 of the superiority die?
@JeremyECrawford Great Weapon Fighting works only with the damage dice of the qualifying weapon.
@<> What if you’ve got a weird situation like a greatsword flametongue or frostbrand? Still only the 2d6 from the greatsword?
@JeremyECrawford Those are weapons. Their dice are affected.
@<> Sorry, to clarify just in case. 2d6 slashing +2d6 fire (for example). The 2d6 fire damage dice are re-rollable as they are weapon dice?
@JeremyECrawford Yes. The description of the flame tongue (the weapon) even says the sword deals the extra damage.