From owner-freebsd-fs@freebsd.org Mon Feb 11 12:30:41 2019 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 905CD14D591D for ; Mon, 11 Feb 2019 12:30:41 +0000 (UTC) (envelope-from lev@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [IPv6:2610:1c1:1:606c::24b:4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 2B60A6B657 for ; Mon, 11 Feb 2019 12:30:41 +0000 (UTC) (envelope-from lev@FreeBSD.org) Received: from onlyone.not-for.work (onlyone.not-for.work [IPv6:2a01:4f8:201:6350::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) (Authenticated sender: lev/mail) by smtp.freebsd.org (Postfix) with ESMTPSA id C9B8675BF for ; Mon, 11 Feb 2019 12:30:40 +0000 (UTC) (envelope-from lev@FreeBSD.org) Received: from [192.168.23.186] (unknown [89.113.128.32]) (Authenticated sender: lev@serebryakov.spb.ru) by onlyone.not-for.work (Postfix) with ESMTPSA id E16C2B820 for ; Mon, 11 Feb 2019 15:30:37 +0300 (MSK) To: "freebsd-fs@freebsd.org" Reply-To: lev@FreeBSD.org From: Lev Serebryakov Subject: Looks like ZFS ARC is broken for 2.5 years. Could somebody ZFS-competent confirm or dismiss? 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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--