> -----Original Message-----
> From: Bie, Tiwei
> Sent: Thursday, September 26, 2019 1:32 PM
> To: Liu, Yong <yong....@intel.com>
> Cc: maxime.coque...@redhat.com; Wang, Zhihong <zhihong.w...@intel.com>;
> step...@networkplumber.org; gavin...@arm.com; dev@dpdk.org
> Subject: Re: [PATCH v3 13/15] vhost: cache address translation result
>
> On Thu, Sep 26, 2019 at 01:13:27AM +0800, Marvin Liu wrote:
> > Cache address translation result and use it in next translation. Due
> > to limited regions are supported, buffers are most likely in same
> > region when doing data transmission.
> >
> > Signed-off-by: Marvin Liu <yong....@intel.com>
> >
> > diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
> > index 7fb172912..d90235cd6 100644
> > --- a/lib/librte_vhost/rte_vhost.h
> > +++ b/lib/librte_vhost/rte_vhost.h
> > @@ -91,10 +91,18 @@ struct rte_vhost_mem_region {
> > int fd;
> > };
> >
> > +struct rte_vhost_mem_region_cache {
> > + uint64_t guest_phys_addr;
> > + uint64_t guest_phys_addr_end;
> > + int64_t host_user_addr_offset;
> > + uint64_t size;
> > +};
> > +
> > /**
> > * Memory structure includes region and mapping information.
> > */
> > struct rte_vhost_memory {
> > + struct rte_vhost_mem_region_cache cache_region;
>
> This breaks ABI.
>
Got, will remove it as no clear performance gain with this patch.
> > uint32_t nregions;
> > struct rte_vhost_mem_region regions[];
> > };
> > @@ -232,11 +240,30 @@ rte_vhost_va_from_guest_pa(struct rte_vhost_memory
> *mem,
> > struct rte_vhost_mem_region *r;
> > uint32_t i;
> >
> > + struct rte_vhost_mem_region_cache *r_cache;
> > + /* check with cached region */
> > + r_cache = &mem->cache_region;
> > + if (likely(gpa >= r_cache->guest_phys_addr && gpa <
> > + r_cache->guest_phys_addr_end)) {
> > + if (unlikely(*len > r_cache->guest_phys_addr_end - gpa))
> > + *len = r_cache->guest_phys_addr_end - gpa;
> > +
> > + return gpa - r_cache->host_user_addr_offset;
> > + }
>
> Does this help a lot in performance?
> We can implement this caching for builtin backend first.
>
Tiwei,
It won’t help too much in performance as region number will be 1 at most of
times.
Will remove cache function in next version.
Thanks,
Marvin
>
> > +
> > +
> > for (i = 0; i < mem->nregions; i++) {
> > r = &mem->regions[i];
> > if (gpa >= r->guest_phys_addr &&
> > gpa < r->guest_phys_addr + r->size) {
> >
> > + r_cache->guest_phys_addr = r->guest_phys_addr;
> > + r_cache->guest_phys_addr_end = r->guest_phys_addr +
> > + r->size;
> > + r_cache->size = r->size;
> > + r_cache->host_user_addr_offset = r->guest_phys_addr -
> > + r->host_user_addr;
> > +
> > if (unlikely(*len > r->guest_phys_addr + r->size - gpa))
> > *len = r->guest_phys_addr + r->size - gpa;
> >
> > --
> > 2.17.1
> >
