Date: Sat, 8 Sep 2018 01:36:29 -0700 From: Mark Millard <marklmi@yahoo.com> To: Kirk McKusick <mckusick@mckusick.com> Cc: bob prohaska <fbsd@www.zefox.net>, FreeBSD Filesystems <freebsd-fs@FreeBSD.org> Subject: Re: CFT: TRIM Consolodation on UFS/FFS filesystems Message-ID: <D2E536B0-B278-4E76-A3A4-3444BF840722@yahoo.com> In-Reply-To: <B9914A0D-69DC-4D3F-9BA4-D180462B2FA5@yahoo.com> References: <201809062330.w86NUphJ027262@chez.mckusick.com> <B9914A0D-69DC-4D3F-9BA4-D180462B2FA5@yahoo.com>
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Just an FYI. I figured out a hack that allows the e.MMC on a microsd card adapter to be used to boot and operate the Pine64+ 2GB, in DDR52 mode at that. (And so shows what was missing in the FreeBSD operation even if the code change is not the proper form of an official fix.) But in the process I discovered that FreeBSD is using (for e.MMC in this tested context): mmc0: REQUEST: CMD38 arg 0x1 flags 0x1d That "0x1" means: TRIM that forces reads of zeros: the true Data Removal command for mmc protocol, a form of erase. 0x3 would be DISCARD, the "performance command" that does not guarantee what would be read afterwards: no erase required. TRIM is older (added in e/MCC 4.4). DISCARD is newer (added in e.MMC 4.5). Each is mandatory when the version has the function at all. Does FreeBSD have a policy of preferring erasure when there is also the option to not require it? === Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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