Re: Discard support (was Re: [PATCH] swap: send callback when swap slot is freed)

John Robinson wrote:
..

I'm slightly out of my depth here, but: if a single TRIM is issued, which apparently returns quickly, can one then revert to issuing ordinary commands like reads and writes and have them complete as quickly as they normally do, or does any following command have to wait until the trim completes? This could be useful if it turned out we won't stall these devices as long as we don't issue more than one TRIM every few seconds; we could keep a TRIM coalesce queue down to being (say) 5 seconds long (or at least, a configurable small number of seconds).

..

I have not attempted to instrument that, but I suspect that any
command after the TRIM has to wait.  Don't know for sure until
somebody measures it though.

One thing I do know, is that Matthew's first cut of TRIM support
means it takes half an hour to do "rm -r" on a kernel source tree.

-ml