Andrew Morton <[EMAIL PROTECTED]> wrote: > > Peter Chubb <[EMAIL PROTECTED]> wrote: > > > > > > Hi, > > As part of the Gelato scalability focus group, we've been running > > OSDL's Re-AIM7 benchmark with an I/O intensive load with varying > > numbers of processors. The current kernel shows severe contention on > > the tree_lock in the address space structure when running on tmpfs or > > ext2 on a RAM disk. > > > > Yup. > > Problem is, an rwlock is a little bit slower than a spinlock on a P4 due to > the buslocked unlock, and a lot of people have p4's. > > Could you do some testing on a 2-way p4?
hm, turns out I did some P4 testing ages ago: with: dd if=/dev/zero of=foo bs=1 count=2M 0.80s user 4.15s system 99% cpu 4.961 total dd if=/dev/zero of=foo bs=1 count=2M 0.73s user 4.26s system 100% cpu 4.987 total dd if=/dev/zero of=foo bs=1 count=2M 0.79s user 4.25s system 100% cpu 5.034 total dd if=foo of=/dev/null bs=1 0.80s user 3.12s system 99% cpu 3.928 total dd if=foo of=/dev/null bs=1 0.77s user 3.15s system 100% cpu 3.914 total dd if=foo of=/dev/null bs=1 0.92s user 3.02s system 100% cpu 3.935 total (3.926: 1.87 usecs) without: dd if=/dev/zero of=foo bs=1 count=2M 0.85s user 3.92s system 99% cpu 4.780 total dd if=/dev/zero of=foo bs=1 count=2M 0.78s user 4.02s system 100% cpu 4.789 total dd if=/dev/zero of=foo bs=1 count=2M 0.82s user 3.94s system 99% cpu 4.763 total dd if=/dev/zero of=foo bs=1 count=2M 0.71s user 4.10s system 99% cpu 4.810 tota dd if=foo of=/dev/null bs=1 0.76s user 2.68s system 100% cpu 3.438 total dd if=foo of=/dev/null bs=1 0.74s user 2.72s system 99% cpu 3.465 total dd if=foo of=/dev/null bs=1 0.67s user 2.82s system 100% cpu 3.489 total dd if=foo of=/dev/null bs=1 0.70s user 2.62s system 99% cpu 3.326 total (3.430: 1.635 usecs) So the spinlock->rwlock conversion costs us 240 nsecs on a one-byte-write. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
