Date: Thu, 18 Feb 2021 20:37:51 -0700 From: Alan Somers <asomers@freebsd.org> To: Alexander Motin <mav@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 812c9f48a2b7 - main - Save context switch per I/O for iSCSI and IOCTL frontends. Message-ID: <CAOtMX2ih2hZZMyKOA4rMG3=ZiWKFw6krYyx9DES1m2p5t8-P1g@mail.gmail.com> In-Reply-To: <202102190329.11J3TgmF088194@gitrepo.freebsd.org> References: <202102190329.11J3TgmF088194@gitrepo.freebsd.org>
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On Thu, Feb 18, 2021 at 8:29 PM Alexander Motin <mav@freebsd.org> wrote: > The branch main has been updated by mav: > > URL: > https://cgit.FreeBSD.org/src/commit/?id=812c9f48a2b7bccc31b2a6077b299822357832e4 > > commit 812c9f48a2b7bccc31b2a6077b299822357832e4 > Author: Alexander Motin <mav@FreeBSD.org> > AuthorDate: 2021-02-19 03:07:32 +0000 > Commit: Alexander Motin <mav@FreeBSD.org> > CommitDate: 2021-02-19 03:29:38 +0000 > > Save context switch per I/O for iSCSI and IOCTL frontends. > > Introduce new CTL core KPI ctl_run(), preprocessing I/Os in the caller > context instead of scheduling another thread just for that. This call > may sleep, that is not acceptable for some frontends like the original > CAM/FC one, but iSCSI already has separate sleepable per-connection RX > threads, and another thread scheduling is mostly just a waste of time. > IOCTL frontend actually waits for the I/O completion in the caller > thread, so the use of another thread for this has even less sense. > > With this change I can measure ~5% IOPS improvement on 4KB iSCSI I/Os > to ZFS. > Cool! That sounds very useful.
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