Date: Wed, 22 Nov 2017 10:44:44 -0700 From: "Justin T. Gibbs" <gibbs@scsiguy.com> To: Alan Somers <asomers@freebsd.org> Cc: Ronald Klop <ronald-lists@klop.ws>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "Justin T. Gibbs" <gibbs@freebsd.org> Subject: Re: svn commit: r326036 - head/sys/cam/scsi Message-ID: <B67D70C6-5695-4DCD-BE29-D3664A653936@scsiguy.com> In-Reply-To: <CAOtMX2gkCE-bVqbpd8K0erOGqp_dk5OJ0QKz_Jqc_SE99Dda_w@mail.gmail.com> References: <201711202227.vAKMRYvW001932@repo.freebsd.org> <op.y92k58c9kndu52@klop.ws> <CAOtMX2gkCE-bVqbpd8K0erOGqp_dk5OJ0QKz_Jqc_SE99Dda_w@mail.gmail.com>
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I'm sure it was to improve the performance of some SSD we were testing = at Spectra. -- Justin > On Nov 22, 2017, at 9:16 AM, Alan Somers <asomers@freebsd.org> wrote: >=20 > I believe the original motivation was to reduce FLUSH CACHE EXT > activity with some old SSDs that handled that command very slowly. > gibbs might know more. >=20 > On Tue, Nov 21, 2017 at 1:14 PM, Ronald Klop <ronald-lists@klop.ws> = wrote: >> Out of curiosity, What is the use case which this improves? Does = happen in >> daily usage or mostly in testing? >>=20 >> Regards, >> Ronald. >>=20 >>=20 >>=20 >> On Mon, 20 Nov 2017 23:27:34 +0100, Alan Somers <asomers@freebsd.org> = wrote: >>=20 >>> Author: asomers >>> Date: Mon Nov 20 22:27:33 2017 >>> New Revision: 326036 >>> URL: https://svnweb.freebsd.org/changeset/base/326036 >>>=20 >>> Log: >>> da(4): Short-circuit unnecessary BIO_FLUSH commands >>> sys/cam/scsi/scsi_da.c >>> Complete BIO_FLUSH commands immediately if the da(4) device = hasn't >>> been written to since the last flush. If we haven't written = to the >>> device, there is no reason to send a flush. >>> Submitted by: gibbs >>> Reviewed by: imp >>> MFC after: 3 weeks >>> Sponsored by: Spectra Logic Corp >>> Differential Revision: https://reviews.freebsd.org/D13106 >>>=20 >>> Modified: >>> head/sys/cam/scsi/scsi_da.c >>>=20 >>> Modified: head/sys/cam/scsi/scsi_da.c >>>=20 >>> = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D >>> --- head/sys/cam/scsi/scsi_da.c Mon Nov 20 22:18:24 2017 = (r326035) >>> +++ head/sys/cam/scsi/scsi_da.c Mon Nov 20 22:27:33 2017 = (r326036) >>> @@ -3038,6 +3038,18 @@ more: >>> } >>> case BIO_FLUSH: >>> /* >>> + * If we don't support sync cache, or the = disk >>> + * isn't dirty, FLUSH is a no-op. Use the >>> + * allocated * CCB for the next bio if one = is >>> + * available. >>> + */ >>> + if ((softc->quirks & DA_Q_NO_SYNC_CACHE) !=3D = 0 || >>> + (softc->flags & DA_FLAG_DIRTY) =3D=3D 0) = { >>> + biodone(bp); >>> + goto skipstate; >>> + } >>> + >>> + /* >>> * BIO_FLUSH doesn't currently communicate >>> * range data, so we synchronize the cache >>> * over the whole disk. We also force >>> @@ -3052,6 +3064,15 @@ more: >>> /*lb_count*/0, >>> SSD_FULL_SIZE, >>> = da_default_timeout*1000); >>> + /* >>> + * Clear the dirty flag before sending the >>> command. >>> + * Either this sync cache will be = successful, or >>> it >>> + * will fail after a retry. If it fails, it = is >>> + * unlikely to be successful if retried = later, so >>> + * we'll save ourselves time by just marking = the >>> + * device clean. >>> + */ >>> + softc->flags &=3D ~DA_FLAG_DIRTY; >>> break; >>> case BIO_ZONE: { >>> int error, queue_ccb; >>> _______________________________________________ >>> svn-src-all@freebsd.org mailing list >>> https://lists.freebsd.org/mailman/listinfo/svn-src-all >>> To unsubscribe, send any mail to = "svn-src-all-unsubscribe@freebsd.org" >=20
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