transfering pages from user space to user space
Hi: I am working on a project to copy (page aligned) the buffer content of one process to the buffer of other process. Now I resolved this issue using copy_page() but, analizing performance with different buffer sizes, the "copy_page" becames the critical time component and limiting factor. I read some articles about, COW, zero copy and page flipping and I wrote a kernel code to implement page "transfer" (only copy page references), but that code fail and hang. The kernel I use is 2.6.32. The pseudocode I think is: pte_t *src_pte, *dst_pte; src_pte = getpte(src_task); dst_pte = getpte(dst_task); free_pte(dst_pte);/*to free the page referenced by this PTE */ *dst_pte = *src_pte; /*copy source PTE to destination PTE */ And here is code added to the kernel: - len = PAGE_SIZE; src_vma=find_vma_intersection(src_proc->p_task->mm,src_addr,src_addr+len); dst_vma=find_vma_intersection(dst_proc->p_task->mm,dst_addr,dst_addr+len); src_pgd=pgd_offset(src_proc->p_task->mm, (unsigned long) src_addr); src_pud=pud_offset(src_pgd,(unsigned long) src_addr); src_pmd=pmd_offset(src_pud,(unsigned long) src_addr); src_pte=pte_offset_map_lock(src_proc->p_task->mm, src_pmd,(unsigned long) src_addr, &src_ptl); dst_pgd=pgd_offset(dst_proc->p_task->mm, (unsigned long) dst_addr); dst_pud=pud_offset(dst_pgd,(unsigned long) dst_addr); dst_pmd=pmd_offset(dst_pud,(unsigned long) dst_addr); dst_pte=pte_offset_map_lock(dst_proc->p_task->mm, dst_pmd,(unsigned long) dst_addr, &dst_ptl); pte_free(dst_proc->p_task->mm, dst_pte); copy_pte_range(dst_proc->p_task->mm, src_proc->p_task->mm, dst_pmd, src_pmd, dst_vma, (unsigned long) dst_addr, ((unsigned long)dst_addr+PAGE_SIZE)); spin_unlock(src_ptl); spin_unlock(dst_ptl); - There are a lots of kernel functions that are not well documented or they have been changed. Can anybody help me with this issue? Does COW (Copy On Write) will make the copy when the processes will modify their buffers? I am not suscribed to the mailing list, please CC: the answers to this email account. Thanks in Advance. I apologize for my basic English. Pablo Pessolani PD: once finishing with that code, some issues about page protection will be considered. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re:
On Wed, Dec 5, 2012 at 1:48 PM, Niroj Pokhrel wrote: > Hi, > I'm trying to work on android audio (pcm_native.c) but got stuck in some > parameters like start threshold, stop threshold, silence zone, silence > threshold. Can anybody please elaborate on what they are each used for ?? > > Please always use a subject line. This question probably belongs to android mailing list or linux-sound mailing list. There is some info in the header about silence_threshold: http://lxr.free-electrons.com/source/include/sound/pcm.h#L306 -- Thank you Warm Regards Anuz ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
[no subject]
Hi, I'm trying to work on android audio (pcm_native.c) but got stuck in some parameters like start threshold, stop threshold, silence zone, silence threshold. Can anybody please elaborate on what they are each used for ?? -- Niroj Pokhrel Software Engineer, Samsung India Software Operations ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Max open file limit
Look at the include/asm-generic/resource.h On 12/5/12, Denis Kirjanov wrote: > #define INR_OPEN_CUR 1024 /* Initial setting for nfile rlimits */ > > > On 12/5/12, Vijay Chauhan wrote: >> Hello, >> >> How many files a process can open at a time? Is it configurable? >> >> I found following in the kernel code: >> >> .. >> .max_fds= NR_OPEN_DEFAULT, >> .. >> .. >> #define NR_OPEN_DEFAULT BITS_PER_LONG >> .. >> .. >> #ifdef __KERNEL__ >> #define BITS_PER_LONG 32 >> .. >> >> But I can open more than 32 files in my user space program. >> >> Thank you, >> Vijay >> >> ___ >> Kernelnewbies mailing list >> Kernelnewbies@kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > > > -- > Regards, > Denis > -- Regards, Denis ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Max open file limit
#define INR_OPEN_CUR 1024 /* Initial setting for nfile rlimits */ On 12/5/12, Vijay Chauhan wrote: > Hello, > > How many files a process can open at a time? Is it configurable? > > I found following in the kernel code: > > .. > .max_fds= NR_OPEN_DEFAULT, > .. > .. > #define NR_OPEN_DEFAULT BITS_PER_LONG > .. > .. > #ifdef __KERNEL__ > #define BITS_PER_LONG 32 > .. > > But I can open more than 32 files in my user space program. > > Thank you, > Vijay > > ___ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- Regards, Denis ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Max open file limit
Well this is not really a limit on number of files, rather a memory allocation optimization for fd_array. The limit you are looking for is: int sysctl_nr_open __read_mostly = 1024*1024; $ cat /proc/sys/fs/nr_open 1048576 -Rajat On Wed, Dec 5, 2012 at 4:38 PM, Vijay Chauhan wrote: > Hello, > > How many files a process can open at a time? Is it configurable? > > I found following in the kernel code: > > .. > .max_fds= NR_OPEN_DEFAULT, > .. > .. > #define NR_OPEN_DEFAULT BITS_PER_LONG > .. > .. > #ifdef __KERNEL__ > #define BITS_PER_LONG 32 > .. > > But I can open more than 32 files in my user space program. > > Thank you, > Vijay > > ___ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Max open file limit
Hello, How many files a process can open at a time? Is it configurable? I found following in the kernel code: .. .max_fds= NR_OPEN_DEFAULT, .. .. #define NR_OPEN_DEFAULT BITS_PER_LONG .. .. #ifdef __KERNEL__ #define BITS_PER_LONG 32 .. But I can open more than 32 files in my user space program. Thank you, Vijay ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
