On 2012-11-27 06:57, Jeff Chua wrote: > On Sun, Nov 25, 2012 at 7:23 AM, Jeff Chua <jeff.chua.linux@xxxxxxxxx> wrote: >> On Sun, Nov 25, 2012 at 5:09 AM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: >>> So it's better to slow down mount. >> >> I am quite proud of the linux boot time pitting against other OS. Even >> with 10 partitions. Linux can boot up in just a few seconds, but now >> you're saying that we need to do this semaphore check at boot up. By >> doing so, it's inducing additional 4 seconds during boot up. > > By the way, I'm using a pretty fast SSD (Samsung PM830) and fast CPU > (2.8GHz). I wonder if those on slower hard disk or slower CPU, what > kind of degradation would this cause or just the same? It'd likely be the same slow down time wise, but as a percentage it would appear smaller on a slower disk. Could you please test Mikulas' suggestion of changing synchronize_sched() in include/linux/percpu-rwsem.h to synchronize_sched_expedited()? linux-next also has a re-write of the per-cpu rw sems, out of Andrews tree. It would be a good data point it you could test that, too. In any case, the slow down definitely isn't acceptable. Fixing an obscure issue like block sizes changing while O_DIRECT is in flight definitely does NOT warrant a mount slow down. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
