Date: Wed, 26 Aug 2020 01:15:50 -0400 From: Zaphod Beeblebrox <zbeeble@gmail.com> To: Allan Jude <allanjude@freebsd.org> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Boot time TRIM ? Message-ID: <CACpH0MfmBMipN5Znusk_AhtUcYaypS0ZtvPaN5GgXvN1TZm39w@mail.gmail.com> In-Reply-To: <924f4c6e-f07e-99fb-ac4a-924efbd3dba3@freebsd.org> References: <CACpH0Me7dj%2BguVJu_%2BAUAYF60ZKtf8aR31bXFEYsU%2B93SunSJg@mail.gmail.com> <CANCZdfo_-E-rXn8OYYraZkbgKBeevvR=bEjX7atwOj6Jru=h8w@mail.gmail.com> <924f4c6e-f07e-99fb-ac4a-924efbd3dba3@freebsd.org>
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On Tue, Aug 25, 2020 at 10:07 PM Allan Jude <allanjude@freebsd.org> wrote: > Note, as of the import last night, the version of OpenZFS in FreeBSD now > supports a persistent L2ARC (cache) device. So on boot, it will > reprocess the list of buffers in the cache device and repopulate the ARC. > > So for a cache device, there is not much point in worrying about TRIM > across reboots. > > For the SLOG device, you basically overwrite the same blocks repeatedly, > and TRIM is likely a waste of time. You might be better off > under-provisioning instead. There really isn't much use for more than 16 > or 32 GB of SLOG anyway. > > This is good news. How long until we see that in 12.x if at all? I think the performance of my L2ARC is going to get a good bump when this comes online. In reaction to others, the NVME has swap, 2 logs and one cache. The logs are both 24G, the swap is 64G and the cache is the rest. When building poudriere it seems to write between 1T and 2T per day in total. The swap is lightly used. 6 or 7 percent --- the swap size is equal to the memory size at 64G right now. Obviously my concern is that TRIM'd stuff doesn't need to move from MLC to TLC or whathaveyou. Even after a reboot.
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