similar to: [PATCH net] Revert "vhost: cache used event for better performance"

This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it was reported to break vhost_net. We want to cache used event and use it to check for notification. The assumption was that guest won't move the event idx back, but this could happen in fact when 16 bit index wraps around after 64K entries. Signed-off-by: Jason Wang <jasowang at redhat.com> --- - Changes from V1:

This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it was reported to break vhost_net. We want to cache used event and use it to check for notification. The assumption was that guest won't move the event idx back, but this could happen in fact when 16 bit index wraps around after 64K entries. Signed-off-by: Jason Wang <jasowang at redhat.com> --- - Changes from V1:

On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: > This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it > was reported to break vhost_net. We want to cache used event and use > it to check for notification. We try to valid cached used event by > checking whether or not it was ahead of new, but this is not correct > all the time, it could be stale and

On Wed, Jul 26, 2017 at 09:37:15PM +0800, Jason Wang wrote: > > > On 2017?07?26? 21:18, Jason Wang wrote: > > > > > > On 2017?07?26? 20:57, Michael S. Tsirkin wrote: > > > On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: > > > > This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it > > > > was reported to

On Wed, Jul 26, 2017 at 09:37:15PM +0800, Jason Wang wrote: > > > On 2017?07?26? 21:18, Jason Wang wrote: > > > > > > On 2017?07?26? 20:57, Michael S. Tsirkin wrote: > > > On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: > > > > This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it > > > > was reported to

On 2017?07?26? 20:57, Michael S. Tsirkin wrote: > On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: >> This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it >> was reported to break vhost_net. We want to cache used event and use >> it to check for notification. We try to valid cached used event by >> checking whether or not it was ahead of new,

On 2017?07?26? 20:57, Michael S. Tsirkin wrote: > On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: >> This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it >> was reported to break vhost_net. We want to cache used event and use >> it to check for notification. We try to valid cached used event by >> checking whether or not it was ahead of new,

When event index was enabled, we need to fetch used event from userspace memory each time. This userspace fetch (with memory barrier) could be saved sometime when 1) caching used event and 2) if used event is ahead of new and old to new updating does not cross it, we're sure there's no need to notify guest. This will be useful for heavy tx load e.g guest pktgen test with Linux driver

When event index was enabled, we need to fetch used event from userspace memory each time. This userspace fetch (with memory barrier) could be saved sometime when 1) caching used event and 2) if used event is ahead of new and old to new updating does not cross it, we're sure there's no need to notify guest. This will be useful for heavy tx load e.g guest pktgen test with Linux driver

On 2017?07?30? 14:26, K. Den wrote: > On Wed, 2017-07-26 at 19:08 +0300, Michael S. Tsirkin wrote: >> On Wed, Jul 26, 2017 at 09:37:15PM +0800, Jason Wang wrote: >>> >>> On 2017?07?26? 21:18, Jason Wang wrote: >>>> >>>> On 2017?07?26? 20:57, Michael S. Tsirkin wrote: >>>>> On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote:

On 2017?07?30? 14:26, K. Den wrote: > On Wed, 2017-07-26 at 19:08 +0300, Michael S. Tsirkin wrote: >> On Wed, Jul 26, 2017 at 09:37:15PM +0800, Jason Wang wrote: >>> >>> On 2017?07?26? 21:18, Jason Wang wrote: >>>> >>>> On 2017?07?26? 20:57, Michael S. Tsirkin wrote: >>>>> On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote:

On Wed, 2017-07-26 at 19:08 +0300, Michael S. Tsirkin wrote: > On Wed, Jul 26, 2017 at 09:37:15PM +0800, Jason Wang wrote: > > > > > > On 2017?07?26? 21:18, Jason Wang wrote: > > > > > > > > > On 2017?07?26? 20:57, Michael S. Tsirkin wrote: > > > > On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: > > > > >

Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/vhost.c | 93 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 56 insertions(+), 37 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c90f437..4d379ed 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -33,8 +33,8 @@ enum { VHOST_MEMORY_F_LOG = 0x1, };

Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/vhost.c | 93 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 56 insertions(+), 37 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c90f437..4d379ed 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -33,8 +33,8 @@ enum { VHOST_MEMORY_F_LOG = 0x1, };

Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/vhost.c | 93 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 56 insertions(+), 37 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c90f437..4d379ed 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -33,8 +33,8 @@ enum { VHOST_MEMORY_F_LOG = 0x1, };

Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/vhost.c | 93 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 56 insertions(+), 37 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c90f437..4d379ed 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -33,8 +33,8 @@ enum { VHOST_MEMORY_F_LOG = 0x1, };

On 2017?07?26? 21:18, Jason Wang wrote: > > > On 2017?07?26? 20:57, Michael S. Tsirkin wrote: >> On Wed, Jul 26, 2017 at 04:03:17PM +0800, Jason Wang wrote: >>> This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it >>> was reported to break vhost_net. We want to cache used event and use >>> it to check for notification. We try to valid

> On 6 Mar 2019, at 08:18, Jason Wang <jasowang at redhat.com> wrote: > > This is used to hide the metadata address from virtqueue helpers. This > will allow to implement a vmap based fast accessing to metadata. > > Signed-off-by: Jason Wang <jasowang at redhat.com> > --- > drivers/vhost/vhost.c | 94 +++++++++++++++++++++++++++++++++++++++++---------- > 1

> On 6 Mar 2019, at 08:18, Jason Wang <jasowang at redhat.com> wrote: > > This is used to hide the metadata address from virtqueue helpers. This > will allow to implement a vmap based fast accessing to metadata. > > Signed-off-by: Jason Wang <jasowang at redhat.com> > --- > drivers/vhost/vhost.c | 94 +++++++++++++++++++++++++++++++++++++++++---------- > 1

Move vhost.h to include/linux to allow vhost driver out-of-tree compilation. Currently, this cannot be done properly because the vhost header file is in driver/vhost. To distribute a new vhost driver before it is included in the kernel tree, we need to package it using kmod, dkms, ..., and to compile it out-of-tree using headers provided by the distribution's kernel development package.