Date: Fri, 7 Sep 2018 10:55:14 +0200 From: Yamagi Burmeister <lists@yamagi.org> To: freebsd-fs@freebsd.org Subject: Re: ZFS (ARC) performance regression in r321610 Message-ID: <20180907105514.b2601aeaeb8e4f1898322525@yamagi.org> In-Reply-To: <3c6f8c96-6ac9-7257-c8c0-8be2063a7c19@FreeBSD.org> References: <20180827154727.80f92fff9bbc931b37928d43@yamagi.org> <3c6f8c96-6ac9-7257-c8c0-8be2063a7c19@FreeBSD.org>
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--Signature=_Fri__7_Sep_2018_10_55_14_+0200_MH/WoywG1byHdYqT Content-Type: text/plain; charset=US-ASCII Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, I just want a give a short conclusion for this problem. On Mon, 27 Aug 2018 17:19:10 +0300 Lev Serebryakov <lev@FreeBSD.org> wrote: > On 27.08.2018 16:47, Yamagi Burmeister wrote: >=20 > > With this program I was able to bisect the source and identify commit > > r321610 (MFV r318946: 8021 ARC buf data scatter-ization) as the culprit: > > https://svnweb.freebsd.org/base?view=3Drevision&revision=3D321610 > You could try to set "zfs_abd_scatter_enabled =3D 0" via kgdb and repeat > tests to be sure, that this code is a problem. After about 2 weeks with "zfs_abd_scatter_enabled" set to 0 (in form of r338365 merged back to 11.2-RELEASE and vfs.zfs.abd_scatter_enabled set to 0) I can confirm that switching of scattered allocations helps, my performance problems are gone. The system is running fine and zfs-stats looks good. To be clear: Switching off scattered allocations has a very positive effect in this and only this workload. On our other ~100 hosts - some of them MySQL installations with other workload patterns - the scattered allocations are a benefit or at least don't hurt. Regards, Yamagi --=20 Homepage: https://www.yamagi.org Github: https://github.com/yamagi GPG: 0x1D502515 --Signature=_Fri__7_Sep_2018_10_55_14_+0200_MH/WoywG1byHdYqT Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEOXu/lxyufwz0gC5x6xRy5x1QJRUFAluSPPMACgkQ6xRy5x1Q JRUhFA/7Bx8s5WBs9Kui1PEvUqoNNjZIY2M8i6K3wuvSgMoIQRt8RIS6f9RjTVAv Gw0XikJZ+mQV3aXNuvev309IJTOK4lp76QqQWxsgO1165wy9qsXF9V0AXEO9YCmq Am0rgF+GwHwqeqZt7M2jGRer3NGZZlax+bTsjmWkY20k2RPFR1KNU06NB/TEkHh4 KiwFWX4Dl/wTs7ev1oQuBqlDTtCX7XywlPRvxjbDG+UFyz/EQxPexbthm3WtBOiX tNXSaFyMgPFflUbWjm+KxEtlOtpKv7k1ukUHdU7Tvf5VKOMMO2iMVMgz5VTc9FAp v9+/WBo8/BcAFfcLS9IU0pHgidpoj1yzmFY2OAuDcMUjvjxJmAsO9wHztVjHmisW dcTENsOX6MCrmHoXi5vP7pvMoKqkjIe8l1vO8feONFy3Tz9JfYiTToR1yziGOynQ minPTjwGdRAhvmrEDyAwVjOyvX5lxPVHHWKvQPiqXpqeGG5Xj5BG7APi3uQHhsKq pjGHSlnfkMjQFQb0J4UDVS/V9UH7xYE40qwg42Xb5gCnsPNxxaFuQOaAgrgPeHS9 jjGHgXxa3fYUte/FxgUV8ba7Vk9AVBYWRsa2m+zXAJr9sizf8pGunPnMalN9aNTx cvGY31H7Ro6MUEbUEa2yobC0mTsnbKAytXb/U9yz+KM9ahcjhds= =p3+5 -----END PGP SIGNATURE----- --Signature=_Fri__7_Sep_2018_10_55_14_+0200_MH/WoywG1byHdYqT--
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