Bug#907606: fsck takes hours to complete, just due to slow screen output

[Adam Borowski]

On Wed, Jan 05, 2022 at 03:17:50PM +0000, Loorey wrote:
> FSCK is the utility for checking the filesystem for Errors and
> fixing those, of course after an ungraceful shutdown this operation
> can take hours, and of course printing the log will be much faster
> than the actual operation, because fsck fixes the system while also
> logging, and in the other case you are just reading and printing the
> log file.

Yet in so many cases it's this log output that's an order or two of
magnitude slower than actual fsck.  Even a spinner gives 200 seeks per
second, while a good modern disk can do in excess of 2M random reads.
Meanwhile, a 115200 terminal is limited to 180 80-character lines per
second, and fbdev on a high-end GPU is much slower than that.

Cf #991218 which is this same problem from another program.

I don't think there's much point running fsck on boot time on any filesystem
newer than ext2 (ie, Hurd), but if it's being done, there's no point dumping
all these details to the screen where no human can possibly read.

Perhaps we should decrease fsck's verbosity or rate-limit screen output,
discarding excess text?


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