In D9611#198637, @avg wrote:

Essentially, L2ARC periodically writes to every block on the device and that allows to physically move the data around.
That's exactly the reason why I think that TRIM is not needed for L2ARC.
TRIM is useful when we don't need data in some area, but we are not going to overwrite that area, so we need to a way to tell the storage system that it can reuse the physical cells without worrying about any data in them. But if we overwrite that area anyway, then the storage system is automatically aware that the data in those physical cells is obsolete. It's free to choose either those same cells or any different cells for the new data according to the wear leveling algorithms, but that's beside the point.

In D9611#198616, @avg wrote:

My understanding of how L2ARC writing works is this. The code maintains a "hand" (like a clock hand) that points to a disk offset. At the regular intervals a certain space in front of the hand is freed by discarding L2 headers that point to that space and then new buffers are written to that space. Then the hand is moved forward by the appropriate amount.
There is also some freeing of L2 headers when ARC headers are freed, etc. In any case, after some uptime almost the whole cache disk is usually filled with data. And the hand inevitably moves forward. So, every block gets written over sooner or later. I do not see how TRIM helps in that case.
The only scenario where it makes difference, in my humble opinion, is the scenario that @mav described: a worn out disk where the "cheese holes" behind the hand can make some difference for writing new blocks at the hand. But I think that that's too marginal to be important.

In D9611#198582, @mav wrote:

In D9611#198579, @smh wrote:

In scenario #1 the performance of TRIM is also generally good, mitigating the need to avoid doing it.

Is there such thing as good TRIM performance? On my new Samsung 950 NVMe I had to disable TRIM as unusable. Though yes, NVMe driver still probably needs aggregation of TRIM requests to get better numbers.

In scenario #1 the performance of TRIM is also generally good, mitigating the need to avoid doing it.

This can could excessive slow down as the capacity of the disk is reached, however it could be argued that a better mitigation for L2ARC devices would be to use an under-provisioned slice to ensure the SSD controller always has space to work.

Couple of little style nits and I'd like to understand why ENAMETOOLONG error gets turned into success in a few places.

Wouldn't it be better to have 0 (the default) be "use the PhyNum field as a fallback to the mapping logic" as that way at least the device would initialise when mpX_mapping_get_sas_id fails?

Thanks for attacking this Andriy its a big task which really needed some attention.

Apart from the comment this looks good in principle, however I think we need to better understand why retrying the probe works as it feels like where just hiding the real error with this.

This looks reasonable however as you say its potentially racey with multiple renames happening.

I'd like to know why finding the current device would ever fail?

Remove redundent check on <= 0

Nice, do you have metrics on the typical dump size increase?

This looks like it might leave old data in the zpool.cache?

Seems reasonable to me

Missed a few sub indents on the white space fixup.

Fix invalid whitespacing (7 spaces instead of tabs)

Define and init cpu_id using rss_getcpu.

We should get this up-streamed.

Restructure Makefile fix to aid future merges as per ngie's suggestion.

Fix pointer cast issue on arm.armeb.

In D5212#110873, @ngie wrote:

Was there any change to how the operations need to be done in order to call efi_handle_lookup in the amd64/arm64 case on head with a ZFS root?

Almost there. recomparing with our diff the only remaining missing block is the following which comes from between r283882 and r283883:

Fix device_paths_match breakage in last diff caused by late check of media type match.

• Comment new methods.
• Fix possible edge case in device_paths_match.
• Fix failure printf in first path case for load_loader.
• Small flow optimisation in try_boot.
• Rename devpath_strncat -> devpath_strlcat to more closely describe its function in terms of standard string functions.
• Increase devpath_str buffer to 256 as 128 could be could be close.
• Optimise placement of device_paths_match in probe_handle.

• Add SATA devpath node decoding
• Fix and rename msg_path_matches -> device_path_matches
• Add boot1 imgpath debug

Further debugging improvements.

Refactor preferred device so that:

1. Its sticky for all requests, this ensures that boot.config is loaded from the same device / pool as loader.efi.
2. Allows UFS only preferred devices to work correctly.

@imp with the latest set of improved debugging we should be able to see what's loading from where.

• Change boot module loader_path -> filepath to better refect its use.
• Switch devinfo_t.devpath to store the full path instead of final node to aid debugging.
• Improve debug and error output.
• Fix DPRINTF for single argument use.
• Refactor msgpath calculation into seperate methods.

Committed as: https://svnweb.freebsd.org/changeset/base/295051

In D5117#108850, @sbruno wrote:

I should have captured r285592 in the MFC of driver version 3.1.0 to stable 10. https://svnweb.freebsd.org/base?view=revision&revision=294061

In D5108#108719, @imp wrote:

When I tested this with a USB drive that had a /boot.config with -h and a SATA SSD with a boot.config with -D in it. The sata was fs0: in the uefi shell , while the usb clocked in with fs1. I get identical boot behavior if I type in fs0:\efi\boot\bootx64.efi and fs1:\efi\boot\bootx64.efi. Both of them are dying during boot because there's no /dev/ada0 to satisfy the /etc/fstab I have on the usb drive. If I pull it out, it goes back to booting correctly.

So it appears that we're now finding the loader.efi, but that at least boot1 is still confused a bit. Perhaps my hack for the /boot.config stuff in there needs to be fixed too, since it clearly is finding the loader.efi.

Anything I can do to help debug this?