What happens if mempool grows huge?

[boogersguy]

Noticing the mempool is around 175MB right now and wondering how bitcoin core nodes handle the case if it grows too large (500mb - 1gb).  Is there a hard limit at which point all new transactions are basically rejected? Or does the software flush older transactions in order to accept new.  What is the MB limit?

[DooMAD]

Technically, there's no "limit" in the same way as there's no single, unified "mempool".  Each node maintains its own individual mempool, so all depends on what each individual node can cope with.  Users with full nodes can change their preferences in that regard via customised configurations.  However, the default setting for most nodes is 300MB, so we should be a little concerned if we approach that size on average across the network.

[pebwindkraft]

Pieter Wuille explained in a stack exchange task, that since version 12 the bitcoin core software can expire transactions, which are longer than 72 hours in the mempool. This would keep the mempool fresh.

[PVminer]

However, the default setting for most nodes is 300MB, so we should be a little concerned if we approach that size on average across the network.

There is no danger except a "danger" of large fees. Bitcoin Core will remove the low-paying transaction from the mempool so there is no way the memory gets exhausted. And actually, we crossed the 300 MB mark. My node (configured up to 600 MB) is currently at 490 MB usage.

[mda]

If bitcoin network becomes congested again then another chain is split from the last one (or some kind of lottery is employed) and so on.

[jnano]

And actually, we crossed the 300 MB mark. My node (configured up to 600 MB) is currently at 490 MB usage.

Do different nodes use different memory formats? The stat sites I've checked, like Johoe's or BTC.com, peaked at just approximately 180MB.

[PVminer]

And actually, we crossed the 300 MB mark. My node (configured up to 600 MB) is currently at 490 MB usage.

Do different nodes use different memory formats? The stat sites I've checked, like Johoe's or BTC.com, peaked at just approximately 180MB.

The node memory usage is larger than the raw transactions size  due to some bookkeeping overhead. The sites report raw size while nodes have real usage limits. 300 MB standard limit is the real one, including the overhead and it has been crossed already, though it is slowly trending down (445 MB right now for my node).

[btctousd81]

more memory gets alloted for mempool.,
i read in source , there is limit of ~400 mb., but it does not stops bitcoin-core to use more memory in case of 400 mb gets full.