Re: [dpdk-dev] [PATCH] mem: get physical address of any pointer

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Thomas,

Please find some comments below.

 > +/**
 > + * Get physical address of any mapped virtual address in the current 
process.
 > + * It is found by browsing the /proc/self/pagemap special file.
 > + * The page won't be swappable anymore.
 > + */
 > +phys_addr_t rte_mem_virt2phy(const void *virt);
 >
 > [...]
 > -static int
 > -find_physaddr(struct hugepage *hugepg_tbl, struct hugepage_info *hpi)
 > +phys_addr_t
 > +rte_mem_virt2phy(const void *virt)
 >   {
 > [...]
 > +    /* allocate page in physical memory and prevent from swapping */
 > +    mlock((void*)aligned, page_size);

Should this function really do the mlock() ?

It's a bit confusing to have a function that looks like a "get"
that will change the status of the page.

Another approach that sounds more reasonnable to me is to let the
application does the mlock(), and have the rte_mem_virt2phy() return
RTE_BAD_PHYS_ADDR if the page is not locked in memory. This info
is well known from the /proc/self/pagemap.

Should we also rename virt2phy in virt2phys ?

Regards,
Olivier