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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...

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...

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 >> bu...

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 >> bu...

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 per...

On Wed, Apr 08, 2015 at 07:41:49AM -0700, Alexander 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 uni...

This patch is ported one from 534:77db69c38249 of linux-2.6.18-xen.hg. Use wmb instead of rmb to enforce ordering between evtchn_upcall_pending and evtchn_pending_sel stores in xen_evtchn_do_upcall(). Cc: Samuel Thibault <samuel.thibault at eu.citrix.com> Signed-off-by: Isaku Yamahata <yamahata at valinux.co.jp> --- drivers/xen/events.c | 2 +- 1 files changed, 1 insertions...

...--git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > index 2b3c228..0245bbe 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -5116,7 +5116,14 @@ sub process { > ? } > ? } > ?# check for memory barriers without a comment. > - if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) { > + > + my @barriers = ('mb', 'rmb', 'wmb', 'read_barrier_depends'); > + my @smp_barriers = ('smp_store_release', 'smp_load_acquire', 'smp_store_mb'); &...

...--git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > index 2b3c228..0245bbe 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -5116,7 +5116,14 @@ sub process { > ? } > ? } > ?# check for memory barriers without a comment. > - if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) { > + > + my @barriers = ('mb', 'rmb', 'wmb', 'read_barrier_depends'); > + my @smp_barriers = ('smp_store_release', 'smp_load_acquire', 'smp_store_mb'); &...

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 data...

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 data...

mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's 2 to 3 times slower than lock; addl that we use on older CPUs. So let's use the locked variant everywhere. While I was at it, I found some inconsistencies in comments in arch/x86/include/asm/barrier.h The documentation fixes are included first - I verified that they do not change the generated code at all.

mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's 2 to 3 times slower than lock; addl that we use on older CPUs. So let's use the locked variant everywhere. While I was at it, I found some inconsistencies in comments in arch/x86/include/asm/barrier.h The documentation fixes are included first - I verified that they do not change the generated code at all.

...out the RAID check running: [root at r2k1 ~] # iostat -xdmc 1 10 Linux 3.10.0-327.13.1.el7.x86_64 (r2k1) 05/27/16 _x86_64_ (32 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 8.87 0.02 1.28 0.21 0.00 89.62 Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util sdd 0.02 0.55 0.15 27.06 0.03 11.40 859.89 1.02 37.40 36.13 37.41 6.86 18.65 sdf 0.02 0.48 0.15 26.99 0.03 11.40 862.17 0.15 5.56 40.94 5.37...

...It also happens on a machine running 2.0.7. I have searched for this problem and discovered it has been reported in a few mailing lists and newsgroups but there's never a reply :( Please help, I'm really stuck. regards, john -- John Rosauer, Senior Systems Administrator email: jar@rmb.com.au RMB Australia Limited business: +61 2 9251 4177 Level 5, Underwood House, 37-49 Pitt Street fax: +61 2 9256 6246 Sydney, 2000, Australia cell: +61 414 580 723

>From the fedora 19 host: [root@fedora ~]# sg_inq /dev/sdc standard INQUIRY: PQual=0 Device_type=0 RMB=0 version=0x05 [SPC-3] [AERC=0] [TrmTsk=0] NormACA=0 HiSUP=0 Resp_data_format=0 SCCS=1 ACC=0 TPGS=1 3PC=0 Protect=0 [BQue=0] EncServ=0 MultiP=0 [MChngr=0] [ACKREQQ=0] Addr16=0 [RelAdr=0] WBus16=1 Sync=1 Linked=0 [TranDis=0] CmdQue=1 length=36 (0x24) Peripheral devi...

mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's 2 to 3 times slower than lock; addl that we use on older CPUs. So we really should use the locked variant everywhere, except that intel manual says that clflush is only ordered by mfence, so we can't. Note: some callers of clflush seems to assume sfence will order it, so there could be existing bugs around

mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's 2 to 3 times slower than lock; addl that we use on older CPUs. So we really should use the locked variant everywhere, except that intel manual says that clflush is only ordered by mfence, so we can't. Note: some callers of clflush seems to assume sfence will order it, so there could be existing bugs around

On 2016-05-25 19:13, Kelly Lesperance wrote: > Hdparm didn?t get far: > > [root at r1k1 ~] # hdparm -tT /dev/sda > > /dev/sda: > Timing cached reads: Alarm clock > [root at r1k1 ~] # Hi Kelly, Try running 'iostat -xdmc 1'. Look for a single drive that has substantially greater await than ~10msec. If all the drives except one are taking 6-8msec, but one is very

On Thu, Dec 31, 2015 at 09:08:38PM +0200, Michael S. Tsirkin wrote: > This defines __smp_xxx barriers for s390, > for use by virtualization. > > Some smp_xxx barriers are removed as they are > defined correctly by asm-generic/barriers.h > > Note: smp_mb, smp_rmb and smp_wmb are defined as full barriers > unconditionally on this architecture. > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > Acked-by: Arnd Bergmann <arnd at arndb.de> > --- > arch/s390/include/asm/barrier.h | 15 +++++++++------ > 1 file changed,...