Core sometimes stalls syncing blocks when nothing holds it back

[jnano]

Any idea why Core stalls sometimes for no reason when syncing blocks? It's not the first time I see it.

At first it's doing a block every few second or so. Then, suddenly, blocks start taking 2-4 minutes each. There's no HDD activity, no real CPU usage. The log doesn't show anything abnormal.

When it happens I just restart it and it resumes syncing normally. Post restart, it's catching up quickly on a lot of blocks with very little downloading, so the problem appears to be in processing already-downloaded blocks, not a networking logic issue.

This is a few minutes after it started going very slowly:


Post restart, after having synced 200+ more blocks. Only 9MB downloaded for that:


I'm still on v0.15.0.1.

[neurotypical]

I've been suffering from this since the early bitcoin-qt days when I started on bitcoin... huge gaps between download activity.. I have no idea why this happens. While the validation process has gotten faster, these huge gaps still happen. I would tell you to check on your connectivity (open proper ports) but then again as far as I know I have that set up properly myself and these huge gaps where nothing happens are still happening. And indeed when I close it and open it again it starts downloading pretty much right away.

Edit: unquoted OP because he doesn't like it

[jnano]

It doesn't look like a download issue, unless it's just a small bit of data needed in order to be able to start processing blocks already download.

BTW: Why quote the post immediately prior? Just makes the thread more difficult to read, especially with the images.