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User-agent: mu4e 1.5.7; emacs 26.3
From:   Phillip Susi <phill@thesusis.net>
To:     Daniel Vetter <daniel@ffwll.ch>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pavel Machek <pavel@ucw.cz>,
        Randy Dunlap <rdunlap@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-doc\@vger.kernel.org" <linux-doc@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>
Subject: Re: fbcon: remove soft scrollback code (missing Doc. patch)
Date:   Tue, 02 Feb 2021 10:13:14 -0500
In-reply-to: <YBlfKgQ1laQLFqpW@phenom.ffwll.local>
Message-ID: <87wnvqts9g.fsf@vps.thesusis.net>
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Daniel Vetter writes:

> Just a quick comment on this: Since most framebuffers are write-combining,
> and reads from that tend to be ~3 orders of magnitude slower than writes
> (at least on the pile of machines I looked at here, there's big
> differences, and some special streaming cpu instructions to make the
> reading side not so slow).
>
> So scrolling by copying tends to be significantly slower than just
> redrawing everything.

I know this was the case years ago with AGP as iirc, it doubled ( 4x, 8x
) the PCI clock rate but only for writes wasn't it?  I thought this was
no longer an issue with PCIe, but if it is, then I guess I'll go ahead
with cleaning up the dead code and having it re-render with the larger
text buffer.