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How does get_user_pages() pin a process page in Linux?
2019 Community Moderator ElectionHow do “pinned” pages in Linux present (or actually “pin”) themselvesHow does the linux kernel manage less than 1GB physical memory?Walking page tables of a process in LinuxDumping the pfn from /proc/<pid>/pagemap does not give the expected contentGetting a memory physical to pid mapping in linuxHow kernel threaduse memory descriptor(mm_struct) of last ran process in Linux?How are memory read, write, execute permissions enforced in the Linux kernel?Is there a way to use remap_pfn_range() to get hugepages?mmap query on linux platformcan we use virt_to_phys for user space memory in kernel module?How to count the anonymous pages and shared pages for a process in Linux using kernel module
I am trying to pin a Linux process page by using get_user_pages() function in kernel. (I am using Ubuntu 16.04, Linux-4.4.0).
But I am not clear, how does get_user_pages() pin the process page, or how does that pin mean in the funtion's description.
I did following test to check if the page is pinned.
1. A process, called aligned_alloc(0x1000, 0x1000) to allocation a 4KB memory.
2. A kernel module, which will receive a virtual address from a process by ioctl().
3. Once the virtual address is received in kernel module, it is used to call get_user_pages() like this,
res = get_user_pages(current, current->mm, vaddr, 1, 1, 1, &page);
4. The process is sleeping for hours, for me to check the status.
With above steps, from /proc/pid/maps, /proc/pid/smaps, and /proc/meminfo, I could NOT find the locking (or pinning) of the process's virtual address.
I also checked the ref_count of the page struct for the process virtual address, before and after call get_user_pages(), the ref_count is the same (3 in my test case), like below.
[ 7159.432196] Before, page flag = ffff800004004c, count=3
[ 7159.432196] Pinned Got mmaped.
[ 7159.432197] After, page flags = ffff800004004c, count = 3
Did I miss something?
And how does get_user_pages() pin the process pages?
I found a similar question in SO, How do "pinned" pages in Linux present (or actually "pin") themselves, but no answers.
memory-management linux-kernel
asked Mar 7 at 5:15
wangt13wangt13
1499
add a comment |
I am trying to pin a Linux process page by using get_user_pages() function in kernel. (I am using Ubuntu 16.04, Linux-4.4.0).
But I am not clear, how does get_user_pages() pin the process page, or how does that pin mean in the funtion's description.
I did following test to check if the page is pinned.
1. A process, called aligned_alloc(0x1000, 0x1000) to allocation a 4KB memory.
2. A kernel module, which will receive a virtual address from a process by ioctl().
3. Once the virtual address is received in kernel module, it is used to call get_user_pages() like this,
res = get_user_pages(current, current->mm, vaddr, 1, 1, 1, &page);
4. The process is sleeping for hours, for me to check the status.
With above steps, from /proc/pid/maps, /proc/pid/smaps, and /proc/meminfo, I could NOT find the locking (or pinning) of the process's virtual address.
I also checked the ref_count of the page struct for the process virtual address, before and after call get_user_pages(), the ref_count is the same (3 in my test case), like below.
[ 7159.432196] Before, page flag = ffff800004004c, count=3
[ 7159.432196] Pinned Got mmaped.
[ 7159.432197] After, page flags = ffff800004004c, count = 3
Did I miss something?
And how does get_user_pages() pin the process pages?
I found a similar question in SO, How do "pinned" pages in Linux present (or actually "pin") themselves, but no answers.
memory-management linux-kernel
asked Mar 7 at 5:15
wangt13wangt13
1499
add a comment |
I am trying to pin a Linux process page by using get_user_pages() function in kernel. (I am using Ubuntu 16.04, Linux-4.4.0).
But I am not clear, how does get_user_pages() pin the process page, or how does that pin mean in the funtion's description.
I did following test to check if the page is pinned.
1. A process, called aligned_alloc(0x1000, 0x1000) to allocation a 4KB memory.
2. A kernel module, which will receive a virtual address from a process by ioctl().
3. Once the virtual address is received in kernel module, it is used to call get_user_pages() like this,
res = get_user_pages(current, current->mm, vaddr, 1, 1, 1, &page);
4. The process is sleeping for hours, for me to check the status.
With above steps, from /proc/pid/maps, /proc/pid/smaps, and /proc/meminfo, I could NOT find the locking (or pinning) of the process's virtual address.
I also checked the ref_count of the page struct for the process virtual address, before and after call get_user_pages(), the ref_count is the same (3 in my test case), like below.
[ 7159.432196] Before, page flag = ffff800004004c, count=3
[ 7159.432196] Pinned Got mmaped.
[ 7159.432197] After, page flags = ffff800004004c, count = 3
Did I miss something?
And how does get_user_pages() pin the process pages?
I found a similar question in SO, How do "pinned" pages in Linux present (or actually "pin") themselves, but no answers.
memory-management linux-kernel
asked Mar 7 at 5:15
wangt13wangt13
1499
I am trying to pin a Linux process page by using get_user_pages() function in kernel. (I am using Ubuntu 16.04, Linux-4.4.0).
But I am not clear, how does get_user_pages() pin the process page, or how does that pin mean in the funtion's description.
I did following test to check if the page is pinned.
1. A process, called aligned_alloc(0x1000, 0x1000) to allocation a 4KB memory.
2. A kernel module, which will receive a virtual address from a process by ioctl().
3. Once the virtual address is received in kernel module, it is used to call get_user_pages() like this,
res = get_user_pages(current, current->mm, vaddr, 1, 1, 1, &page);
4. The process is sleeping for hours, for me to check the status.
With above steps, from /proc/pid/maps, /proc/pid/smaps, and /proc/meminfo, I could NOT find the locking (or pinning) of the process's virtual address.
I also checked the ref_count of the page struct for the process virtual address, before and after call get_user_pages(), the ref_count is the same (3 in my test case), like below.
[ 7159.432196] Before, page flag = ffff800004004c, count=3
[ 7159.432196] Pinned Got mmaped.
[ 7159.432197] After, page flags = ffff800004004c, count = 3
Did I miss something?
And how does get_user_pages() pin the process pages?
I found a similar question in SO, How do "pinned" pages in Linux present (or actually "pin") themselves, but no answers.
memory-management linux-kernel
memory-management linux-kernel
asked Mar 7 at 5:15
wangt13wangt13
1499
asked Mar 7 at 5:15
wangt13wangt13
1499
asked Mar 7 at 5:15
wangt13wangt13
1499
asked Mar 7 at 5:15
wangt13wangt13
1499
asked Mar 7 at 5:15
wangt13wangt13
1499
1499
add a comment |
add a comment |
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