> -----Original Message----- > From: David Brownell [mailto:[EMAIL PROTECTED] > Sent: den 2 december 2008 21:46 > To: Joakim Tjernlund > Cc: 'Peter Korsgaard'; [email protected] > Subject: Re: [spi-devel-general] Performance of spi_mpc83xx.c sucks. > > On Tuesday 02 December 2008, Joakim Tjernlund wrote: > > > > > > I've not observed polling from a task context to starve anyone, > > > when done sanely. The opposite is true for doing an order of > > > magnitude more instructions in IRQ context ... > > > > When playing with this the app developer complained that the system didn't > > behave as expected so I guessed it had to do with starvation. Perhaps > > lowering the prio or something would be a wise thing to do? Or is the thread > > already at lower prio than normal userspace processes? > > If you're only guessing about what's going on, you need to go > back and get solid data. What does "as expected" mean? Some > app developers have silly expectations. If you were "playing" > the issue could more easily have been goofs in your code.
yeah, I know I need to investigate this further. I just want to put the "starving" issue out of my mind. I feel a bit uneasy about the busy wait nature of polling for potentially long periods of time and that might slow down the rest of the system. he, I just remembered that one of the complaints was that the SPI thread started to consume a lot of CPU when it was polling :) > > > I guess you are not keen on a LOWLAT option for SPI transfers? > > Again, you're guessing in absence of facts ... including a > concrete proposal for what a "LOWLAT option" would be here, > and how it would relate to that one developer's possibly > unrealistic expectations in the context of a collection of > experimental kernel hacks vs. using a saner implementation > of the I/O loops to start with. Here I was thinking LOWLAT as a per transaction flag that would mean that the driver should try to complete the transactions as fast as possible. In my case that would mean polling instead of IRQ driven. I don't have a complete suggestion, just want to test the idea first. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
