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Message-ID: <4D11D939.9080808@cfl.rr.com> Date: Wed, 22 Dec 2010 05:55:53 -0500 From: Mark Hounschell <dmarkh@....rr.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Michael Tokarev <mjt@....msk.ru>, Linux-kernel <linux-kernel@...r.kernel.org>, dri-devel@...ts.freedesktop.org Subject: Re: VERY slow scrolling on radeon graphics card: debugging a timing issue? On 12/22/2010 05:00 AM, Andrew Morton wrote: > (cc dri-devel) > > On Mon, 20 Dec 2010 23:58:21 +0300 Michael Tokarev <mjt@....msk.ru> wrote: > > >> Hello. >> >> A weird problem here, and I'm looking for help in >> an attempt to solve it. >> >> Ever since KMS went into kernel and I tried turning >> it on, the scrolling speed on the resulting "text" >> console (with kms it works in one of graphics modes >> hence "text" in quotes) become really _awful_. >> >> For example, running `dmesg' (which has ~2000 lines) >> on the console takes about 2.5 _minutes_ (!) to >> complete, -- which means the speed is about 10 lines >> per second. On an old notebook I have, with some also >> nvidia card, the same operation completes in about >> 0.8 sec. >> >> The lines goes up in a slow motion, I can watch every >> new line appearing and scrolling. >> >> It was this way for a long time, and I almost gave up -- >> in X everything works ok, and in order to speed up >> booting again I just added "quiet" option to the kernel >> command line, to avoid scrolling of kernel messages. >> >> But yesterday I noticed something else entirely, which >> make me hope the problem actually _can_ be solved. >> >> The thing is: that same scrolling becomes much faster >> when I "do something" else while it scrolls up. First >> I noticed this when I wanted to switch to another vt >> while it were scrolling -- I held down Ctrl key on my >> keyboard, and out of the sudden the scroll speed up >> dramatically. >> >> It turned out I can speed the thing to about 10 times >> by generating some load: hit and hold a key on the >> keyboard (generates interrupts?), run kernel compile >> in the background (generates disk interrupts?), move >> mouse... >> >> While doing "something", the same scrolling completes >> in about 8 seconds instead of 2m30s. Dramatic improvement. >> >> Now, when I hold a key or move mouse, the scrolling >> is "jumpy" - sometimes it slows down back to original >> "slow" form for a bit, and sometimes it jumps a few >> lines in one go. >> >> I tried to disable cpufreq (selecting "performance" >> governor) - this changes exactly nothing. >> >> Next someone suggested the "perf" tool. And this one >> is even more interesting: while `perf top' is running >> (on another console or X), the scrolling is.. fast >> again, as if I were moving my mouse! Once I stop >> `perf top', it becomes slow again. So the bug >> disappears while you watch it. >> >> And there I'm stuck again. I asked in #radeon, but >> there, Alex Deucher told me that he has no clue and >> that the behavour is weird (it is weird indeed). >> >> Any hints on where to go from there are apprecated. >> >> The hardware is an AMD780g-based motherboard with >> and Athlon CPU, I've seen the same behavour from >> many other similar boards. Kernels - all up to >> the current 2.6.36.2, sine the old days when kms >> for radeon first appeared in staging. >> >> I know kms/fbcon scrolling is slow on radeon because >> it uses completely unoptimized bitblt routines (even >> when the hw is pretty much capable of doing all that >> stuff internally). But what I see here is something >> different - the 8 sec to scroll 2000 lines is the >> result from the un-optimal bitblt, not the 2m30s. >> > I also see this very problem on several machines I have with radeon video. For me the worst part is using vi in a konsole. Moving the cursor around is so slow that I just can't use these machines directly and have to ssh into them from another machine just to work on them. I know its probably not proper to mention it, but when I run the ATI proprietary driver, that problem does go away. But for other reasons I can't use it. Regards Mark -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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