On Sun, Feb 10, 2008 at 11:26:06AM +0000, Paul Brook wrote: > On Sunday 10 February 2008, Blue Swirl wrote: > > On 2/9/08, H. Peter Anvin <[EMAIL PROTECTED]> wrote: > > > Blue Swirl wrote: > > > >> If you look at the patch, there are no timing dependencies; the only > > > >> parameter is the depth of the virtual queue. The exhaustion is > > > >> completely controlled by target OS access patterns. > > > > > > > > Thanks, this clarified the difference. But I'll rephrase my original > > > > comment: > > > > > > > > The patch looks OK, but the simulated FIFO exhaustion should benefit > > > > all devices, as > > > > discussed here: > > > > http://lists.gnu.org/archive/html/qemu-devel/2007-12/msg00283.html > > > > > > The difference is you *can't* do that in a general layer. > > > > What makes you think that is impossible? > > IIUC the proposed patch makes the serial driver return an empty FIFO exactly > once, them immediately continue receiving data. Throughput should be > approximately the same, you've just got a bit of extra overhead to process > the additional interrupts. This is very different to the previous patch > which did time-based throughput limiting. > > You can't do this in generic code because there's no way to guess when the > guest os has seen the FIFO empty condition. The best you can do is pause for > some arbitrary length of time, which is both unreliable (the guest OS may not > have got to far enough yet, especially if the host machine is heavily > loaded), and has a significant negative impact on throughput. > > > Also win2k install hack in ide.c seems to be related to this problem, > > so even more generic solution would be desirable. > > IIUC the win2k hack is an actual timing problem. The win2k IDE drivers are > buggy, and fall over if the drive responds too soon. >
Is everybody convinced about this patch now? I would really like to see it in the CVS, as it greatly improves the usability of the serial consoles on targets running GNU/Linux (and probably OSes). -- .''`. Aurelien Jarno | GPG: 1024D/F1BCDB73 : :' : Debian developer | Electrical Engineer `. `' [EMAIL PROTECTED] | [EMAIL PROTECTED] `- people.debian.org/~aurel32 | www.aurel32.net
