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

Mark Lord
2009-08-17T02:05:43Z

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