Date: Mon, 11 Feb 2019 15:30:31 +0300 From: Lev Serebryakov <lev@FreeBSD.org> To: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Looks like ZFS ARC is broken for 2.5 years. Could somebody ZFS-competent confirm or dismiss? Message-ID: <27e55fb1-9258-ecd7-621f-86efa314c694@FreeBSD.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --fjZUZ47NgMCUYGA5xr7vD5tFqxc5pVBcp Content-Type: multipart/mixed; boundary="PjVSUJITWrSzLzUNQgQHOBmqyIzlVmr3f"; protected-headers="v1" From: Lev Serebryakov <lev@FreeBSD.org> Reply-To: lev@FreeBSD.org To: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Message-ID: <27e55fb1-9258-ecd7-621f-86efa314c694@FreeBSD.org> Subject: Looks like ZFS ARC is broken for 2.5 years. Could somebody ZFS-competent confirm or dismiss? --PjVSUJITWrSzLzUNQgQHOBmqyIzlVmr3f Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable One of the strongest features of ZFS is ARC algorithm for cache management. It is still best algorithm for generic-purpose caches, for ~15 years now. But looks like ARC implementation in post-Solaris ZFS broken for 2.5 years now, after adding "compressed ARC". Especially, adaptions on ghost list hits are broken. Look here for details: https://reviews.freebsd.org/D19094 Could somebody more ZFS-aware than me look at this diff? Looks like we (and upstream, too) have huge problem with ARC effectiveness, which is in-line with my gut feeling. --=20 // Lev Serebryakov --PjVSUJITWrSzLzUNQgQHOBmqyIzlVmr3f-- --fjZUZ47NgMCUYGA5xr7vD5tFqxc5pVBcp Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE+W0coLX0MYtnSzMK6rA8WL/cR48FAlxhauxfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEY5 NkQxQ0EwQjVGNDMxOEI2NzRCMzMwQUVBQjAzQzU4QkZEQzQ3OEYACgkQ6rA8WL/c R48imA//bwzS7+GXoTlSDlJGFePwp30AdswqtXctrl0bIJGKX7zqum5EL29Xucl4 64xEdIZJtVXRSTmAZjDcPROMn3M574y+/5b5FTDAJUnkxDzVG0MrN0gAV3A+fDp+ wpy9EWoTYK9J97L2Q0tMkB2UQ6R5LYYkzwnqpy6AWamh8uYoD7Khk4JXuZLqQs/J c66daRqzGxvGOdop3GnrdTj5kxbKM3lQwob/6VQCuOLkkwYynU27lm44nWPgMBvS cbBhIv5aT4Ay+kcqAET5wqO2buDpSgunOvSnFM8Or5XcpC0VMBVs/pCYBe1ZW56b t0R1eRJA/+i/eOBYQ8vhe744jowsp/1aVXq9PoZG4M/wmX9dU+DXV/dEItWU2OmP ozta8nQSIiPHUa60x63G/d6ECaKGssZxrO7FJcj5/PehyZeZvDukj+X81kgwya3i dDeg2tcKJINfpS3SGk83qtjPVIvMtZzK8S9onJhqoPtrbCWLSuhxdxp6evNVJFGZ CxL1poyPkdbcY5CvKAhDQw9n4yZavnh6AP74wFCUr6nwXxe6/6BP6ZlfXB47qElm CYae4DLhKHL3Stdp6zTA6V4ULiw0seXG9bz00p0FN77kEcfPbBpQyGagY1DxvLr/ 2GUlJwYwfhyLo2MgKdq3pfoQScPF+3ata9eilHe0U4dZJwZ7GU8= =NJft -----END PGP SIGNATURE----- --fjZUZ47NgMCUYGA5xr7vD5tFqxc5pVBcp--
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