> On 05 May 2016, at 16:39, Warner Losh <[email protected]> wrote: > >> What do you think? In some cases it’s clear that TRIM can do more harm than >> good. > > I think it’s best we not overreact.
I agree. But with this issue the system is almost unusable for now. > This particular case is cause by the nvd driver, not the Intel P3500 NVME > drive. You need > a solution (3): Fix the driver. > > Specifically, ZFS is pushing down a boatload of BIO_DELETE requests. In > ata/da land, these > requests are queued up, then collapsed together as much as makes sense (or is > possible). > This vastly helps performance (even with the extra sorting that I forced to > be in there that I > need to fix before 11). The nvd driver needs to do the same thing. I understand that, but I don’t think it’s a good that ZFS depends blindly on a driver feature such as that. Of course, it’s great to exploit it. I have also noticed that ZFS has a good throttling mechanism for write operations. A similar mechanism should throttle trim requests so that trim requests don’t clog the whole system. > I’d be extremely hesitant to tossing away TRIMs. They are actually quite > important for > the FTL in the drive’s firmware to proper manage the NAND wear. More free > space always > reduces write amplification. It tends to go as 1 / freespace, so simply > dropping them on > the floor should be done with great reluctance. I understand. I was wondering about choosing the lesser between two evils. A 15 minute I/O stall (I deleted 2 TB of data, that’s a lot, but not so unrealistic) or settings trims aside during the peak activity. I see that I was wrong on that, as a throttling mechanism would be more than enough probably, unless the system is close to running out of space. I’ve filed a bug report anyway. And copying to -stable. https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=209571 Thanks! Borja. _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[email protected]"
