On 4/20/23 11:01 AM, Muhammad Usama Anjum wrote: > +/* Supported flags */ > +#define PM_SCAN_OP_GET (1 << 0) > +#define PM_SCAN_OP_WP (1 << 1) We have only these flag options available in PAGEMAP_SCAN IOCTL. PM_SCAN_OP_GET must always be specified for this IOCTL. PM_SCAN_OP_WP can be specified as need. But PM_SCAN_OP_WP cannot be specified without PM_SCAN_OP_GET. (This was removed after you had asked me to not duplicate functionality which can be achieved by UFFDIO_WRITEPROTECT.) 1) PM_SCAN_OP_GET | PM_SCAN_OP_WP vs 2) UFFDIO_WRITEPROTECT After removing the usage of uffd_wp_range() from PAGEMAP_SCAN IOCTL, we are getting really good performance which is comparable just like we are depending on SOFT_DIRTY flags in the PTE. But when we want to perform wp, PM_SCAN_OP_GET | PM_SCAN_OP_WP is more desirable than UFFDIO_WRITEPROTECT performance and behavior wise. I've got the results from someone else that UFFDIO_WRITEPROTECT block pagefaults somehow which PAGEMAP_IOCTL doesn't. I still need to verify this as I don't have tests comparing them one-to-one. What are your thoughts about it? Have you thought about making UFFDIO_WRITEPROTECT perform better? I'm sorry to mention the word "performance" here. Actually we want better performance to emulate Windows syscall. That is why we are adding this functionality. So either we need to see what can be improved in UFFDIO_WRITEPROTECT or can I please add only PM_SCAN_OP_WP back in pagemap_ioctl? Thank you so much for the help. -- BR, Muhammad Usama Anjum
