search for: dma_wmb

This change makes it so that instead of using smp_wmb/rmb which varies depending on the kernel configuration we can can use dma_wmb/rmb which for most architectures should be equal to or slightly more strict than smp_wmb/rmb. The advantage to this is that these barriers are available to uniprocessor builds as well so the performance should improve under such a configuration. Signed-off-by: Alexander Duyck <alexander.h.duyc...

This change makes it so that instead of using smp_wmb/rmb which varies depending on the kernel configuration we can can use dma_wmb/rmb which for most architectures should be equal to or slightly more strict than smp_wmb/rmb. The advantage to this is that these barriers are available to uniprocessor builds as well so the performance should improve under such a configuration. Signed-off-by: Alexander Duyck <alexander.h.duyc...

On Tue, Apr 07, 2015 at 05:47:42PM -0700, Alexander Duyck wrote: > This change makes it so that instead of using smp_wmb/rmb which varies > depending on the kernel configuration we can can use dma_wmb/rmb which for > most architectures should be equal to or slightly more strict than > smp_wmb/rmb. > > The advantage to this is that these barriers are available to uniprocessor > builds as well so the performance should improve under such a > configuration. > > Signed-off-...

On 04/08/2015 01:42 AM, Michael S. Tsirkin wrote: > On Tue, Apr 07, 2015 at 05:47:42PM -0700, Alexander Duyck wrote: >> This change makes it so that instead of using smp_wmb/rmb which varies >> depending on the kernel configuration we can can use dma_wmb/rmb which for >> most architectures should be equal to or slightly more strict than >> smp_wmb/rmb. >> >> The advantage to this is that these barriers are available to uniprocessor >> builds as well so the performance should improve under such a >> configuration....

On 04/08/2015 01:42 AM, Michael S. Tsirkin wrote: > On Tue, Apr 07, 2015 at 05:47:42PM -0700, Alexander Duyck wrote: >> This change makes it so that instead of using smp_wmb/rmb which varies >> depending on the kernel configuration we can can use dma_wmb/rmb which for >> most architectures should be equal to or slightly more strict than >> smp_wmb/rmb. >> >> The advantage to this is that these barriers are available to uniprocessor >> builds as well so the performance should improve under such a >> configuration....

...r Duyck wrote: > > On 04/08/2015 01:42 AM, Michael S. Tsirkin wrote: > >On Tue, Apr 07, 2015 at 05:47:42PM -0700, Alexander Duyck wrote: > >>This change makes it so that instead of using smp_wmb/rmb which varies > >>depending on the kernel configuration we can can use dma_wmb/rmb which for > >>most architectures should be equal to or slightly more strict than > >>smp_wmb/rmb. > >> > >>The advantage to this is that these barriers are available to uniprocessor > >>builds as well so the performance should improve under such a &g...

virtio is using barriers to order memory accesses, thus dma_wmb/rmb is a good match. Build-tested on x86: Before [mst at tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename 11392 820 0 12212 2fb4 drivers/virtio/virtio_ring.o After mst at tuck linux]$ size drivers/virtio/virtio_ring.o text dat...

virtio is using barriers to order memory accesses, thus dma_wmb/rmb is a good match. Build-tested on x86: Before [mst at tuck linux]$ size drivers/virtio/virtio_ring.o text data bss dec hex filename 11392 820 0 12212 2fb4 drivers/virtio/virtio_ring.o After mst at tuck linux]$ size drivers/virtio/virtio_ring.o text dat...

...ore consistent. To simplify things, you may consider things before the optimization brought in by commit 9e1a27ea42691429e31f158cce6fc61bc79bb2e9 Author: Alexander Duyck <alexander.h.duyck at redhat.com> Date: Mon Apr 13 21:03:49 2015 +0930 virtio_ring: Update weak barriers to use dma_wmb/rmb > As previously stated, smp_mb() does not cover the same memory domains as > dma_mb() would. I know. We used to consistently do the right thing on SMP, but on UP Linux does not have good portable APIs for us to use. So we hack around with what's available which is typically stronge...

...ore consistent. To simplify things, you may consider things before the optimization brought in by commit 9e1a27ea42691429e31f158cce6fc61bc79bb2e9 Author: Alexander Duyck <alexander.h.duyck at redhat.com> Date: Mon Apr 13 21:03:49 2015 +0930 virtio_ring: Update weak barriers to use dma_wmb/rmb > As previously stated, smp_mb() does not cover the same memory domains as > dma_mb() would. I know. We used to consistently do the right thing on SMP, but on UP Linux does not have good portable APIs for us to use. So we hack around with what's available which is typically stronge...

On 01/10/2016 06:18 AM, Michael S. Tsirkin wrote: > On mips dma_rmb, dma_wmb, smp_store_mb, read_barrier_depends, > smp_read_barrier_depends, smp_store_release and smp_load_acquire match > the asm-generic variants exactly. Drop the local definitions and pull in > asm-generic/barrier.h instead. > This statement doesn't fit MIPS barriers variations. Moreover,...

On 01/10/2016 06:18 AM, Michael S. Tsirkin wrote: > On mips dma_rmb, dma_wmb, smp_store_mb, read_barrier_depends, > smp_read_barrier_depends, smp_store_release and smp_load_acquire match > the asm-generic variants exactly. Drop the local definitions and pull in > asm-generic/barrier.h instead. > This statement doesn't fit MIPS barriers variations. Moreover,...

...before > > the optimization brought in by > > commit 9e1a27ea42691429e31f158cce6fc61bc79bb2e9 > > Author: Alexander Duyck <alexander.h.duyck at redhat.com> > > Date: Mon Apr 13 21:03:49 2015 +0930 > > > > virtio_ring: Update weak barriers to use dma_wmb/rmb > > That commit doesn't make any sense. dma_*mb() explicitly does _NOT_ > cover the smp_*mb() part. > > Again, look at the ARM definitions, the smp_*mb() primitives use the > inner coherence stuff, while the dma_*mb() primitives use the outer > coherent stuff. Does o...

...before > > the optimization brought in by > > commit 9e1a27ea42691429e31f158cce6fc61bc79bb2e9 > > Author: Alexander Duyck <alexander.h.duyck at redhat.com> > > Date: Mon Apr 13 21:03:49 2015 +0930 > > > > virtio_ring: Update weak barriers to use dma_wmb/rmb > > That commit doesn't make any sense. dma_*mb() explicitly does _NOT_ > cover the smp_*mb() part. > > Again, look at the ARM definitions, the smp_*mb() primitives use the > inner coherence stuff, while the dma_*mb() primitives use the outer > coherent stuff. Does o...

...f --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h > index c358c31..fbd25b2 100644 > --- a/arch/s390/include/asm/barrier.h > +++ b/arch/s390/include/asm/barrier.h > @@ -26,18 +26,21 @@ > #define wmb() barrier() > #define dma_rmb() mb() > #define dma_wmb() mb() > -#define smp_mb() mb() > -#define smp_rmb() rmb() > -#define smp_wmb() wmb() > - > -#define smp_store_release(p, v) \ > +#define __smp_mb() mb() > +#define __smp_rmb() rmb() > +#define __smp_wmb() wmb() > +#define smp_mb() __smp_mb() > +#d...

...f --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h > index c358c31..fbd25b2 100644 > --- a/arch/s390/include/asm/barrier.h > +++ b/arch/s390/include/asm/barrier.h > @@ -26,18 +26,21 @@ > #define wmb() barrier() > #define dma_rmb() mb() > #define dma_wmb() mb() > -#define smp_mb() mb() > -#define smp_rmb() rmb() > -#define smp_wmb() wmb() > - > -#define smp_store_release(p, v) \ > +#define __smp_mb() mb() > +#define __smp_rmb() rmb() > +#define __smp_wmb() wmb() > +#define smp_mb() __smp_mb() > +#d...

On sparc 64 bit dma_rmb, dma_wmb, smp_store_mb, smp_mb, smp_rmb, smp_wmb, read_barrier_depends and smp_read_barrier_depends match the asm-generic variants exactly. Drop the local definitions and pull in asm-generic/barrier.h instead. nop uses __asm__ __volatile but is otherwise identical to the generic version, drop that as well....

On sparc 64 bit dma_rmb, dma_wmb, smp_store_mb, smp_mb, smp_rmb, smp_wmb, read_barrier_depends and smp_read_barrier_depends match the asm-generic variants exactly. Drop the local definitions and pull in asm-generic/barrier.h instead. nop uses __asm__ __volatile but is otherwise identical to the generic version, drop that as well....

On mips dma_rmb, dma_wmb, smp_store_mb, read_barrier_depends, smp_read_barrier_depends, smp_store_release and smp_load_acquire match the asm-generic variants exactly. Drop the local definitions and pull in asm-generic/barrier.h instead. This is in preparation to refactoring this code area. Signed-off-by: Michael S. Tsir...

On metag dma_rmb, dma_wmb, smp_store_mb, read_barrier_depends, smp_read_barrier_depends, smp_store_release and smp_load_acquire match the asm-generic variants exactly. Drop the local definitions and pull in asm-generic/barrier.h instead. This is in preparation to refactoring this code area. Signed-off-by: Michael S. Tsir...