Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On Thu, Mar 15, 2018 at 9:27 AM, Sinan Kaya wrote: > On 3/15/2018 12:21 PM, Sinan Kaya wrote: >> On 3/15/2018 10:32 AM, Alexander Duyck wrote: >>> We tend to do something like: >>> update tx_buffer_info >>> update tx_desc >>> wmb() >>> point first tx_buffer_info

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On 3/15/2018 12:21 PM, Sinan Kaya wrote: > On 3/15/2018 10:32 AM, Alexander Duyck wrote: >> We tend to do something like: >> update tx_buffer_info >> update tx_desc >> wmb() >> point first tx_buffer_info next_to_watch value at last tx_desc >> update next_to_use >> notify device via

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On 3/15/2018 10:32 AM, Alexander Duyck wrote: > We tend to do something like: > update tx_buffer_info > update tx_desc > wmb() > point first tx_buffer_info next_to_watch value at last tx_desc > update next_to_use > notify device via writel > > We do it this way because we have to

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On Wed, Mar 14, 2018 at 7:17 PM, Sinan Kaya wrote: > On 3/14/2018 9:44 PM, Alexander Duyck wrote: >> On Wed, Mar 14, 2018 at 3:57 PM, Sinan Kaya wrote: >>> Hi Alexander, >>> >>> On 3/14/2018 5:49 PM, Alexander Duyck wrote: On Wed, Mar 14, 2018 at

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On 3/14/2018 9:44 PM, Alexander Duyck wrote: > On Wed, Mar 14, 2018 at 3:57 PM, Sinan Kaya wrote: >> Hi Alexander, >> >> On 3/14/2018 5:49 PM, Alexander Duyck wrote: >>> On Wed, Mar 14, 2018 at 5:13 AM, wrote: On 2018-03-14 01:08, Timur Tabi

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On Tue, Mar 13, 2018 at 8:20 PM, Sinan Kaya wrote: > Code includes wmb() followed by writel() in multiple places. writel() > already has a barrier on some architectures like arm64. > > This ends up CPU observing two barriers back to back before executing the > register

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On Wed, Mar 14, 2018 at 3:57 PM, Sinan Kaya wrote: > Hi Alexander, > > On 3/14/2018 5:49 PM, Alexander Duyck wrote: >> On Wed, Mar 14, 2018 at 5:13 AM, wrote: >>> On 2018-03-14 01:08, Timur Tabi wrote: On 3/13/18 10:20 PM, Sinan Kaya wrote:

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

Hi Alexander, On 3/14/2018 5:49 PM, Alexander Duyck wrote: > On Wed, Mar 14, 2018 at 5:13 AM, wrote: >> On 2018-03-14 01:08, Timur Tabi wrote: >>> >>> On 3/13/18 10:20 PM, Sinan Kaya wrote: > Actually I would argue this whole patch set is pointless. For starters > why is

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On Wed, Mar 14, 2018 at 5:13 AM, wrote: > On 2018-03-14 01:08, Timur Tabi wrote: >> >> On 3/13/18 10:20 PM, Sinan Kaya wrote: >>> >>> +/* Assumes caller has executed a write barrier to order memory and >>> device >>> + * requests. >>> + */ >>> static inline void

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On 2018-03-14 01:08, Timur Tabi wrote: On 3/13/18 10:20 PM, Sinan Kaya wrote: +/* Assumes caller has executed a write barrier to order memory and device + * requests. + */ static inline void ixgbevf_write_tail(struct ixgbevf_ring *ring, u32 value) { - writel(value, ring->tail); +

Re: [PATCH 7/7] ixgbevf: eliminate duplicate barriers on weakly-ordered archs

On 3/13/18 10:20 PM, Sinan Kaya wrote: +/* Assumes caller has executed a write barrier to order memory and device + * requests. + */ static inline void ixgbevf_write_tail(struct ixgbevf_ring *ring, u32 value) { - writel(value, ring->tail); + writel_relaxed(value, ring->tail); }