Date: Sat, 21 Apr 2018 20:25:30 +0000 From: Colin Percival <cperciva@tarsnap.com> To: cem@freebsd.org, Warner Losh <imp@bsdimp.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: RFC: Hiding per-CPU kernel output behind bootverbose Message-ID: <01000162e9e21428-4144fd41-2e1e-4af8-a1b0-ffc0d18fc432-000000@email.amazonses.com> In-Reply-To: <CAG6CVpVfv6SyM5SgCLkyxf=0qenz2s0WpS7AuNSzssK3O0YgaA@mail.gmail.com> References: <01000162df15f856-1e5d2641-2a72-4250-8d8e-adcd47bc5db4-000000@email.amazonses.com> <20180419204405.GE6887@kib.kiev.ua> <CAG6CVpUerOo%2B55nJq61Hy83RYpbOZS6puEDuemspfNS12urZZw@mail.gmail.com> <20180419214550.GF6887@kib.kiev.ua> <01000162e58a4670-66a9983e-c3ef-493a-a60f-c477645b5100-000000@email.amazonses.com> <CANCZdfoNuN%2BECCnTkWufWeGD2HOFbvM4S5eGmDzHV8JGT1M2ag@mail.gmail.com> <CAG6CVpVfv6SyM5SgCLkyxf=0qenz2s0WpS7AuNSzssK3O0YgaA@mail.gmail.com>
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On 04/21/18 11:03, Conrad Meyer wrote: > It sounds like EC2 is redrawing on every character emitted, scrolling > or not. So the additional line breaks shouldn't hurt. EC2 redraws characters when they're written to the VGA text mode buffer. Line breaks absolutely matter -- when we have a line break we rewrite the entire screen. Writing characters without scrolling is much faster. (FWIW, this applies to vt_fb as well; it's just that EC2 is the most extreme case since it combines a large number of CPUs with a slow emulated VGA. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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