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Hi Yann:
Reading the patch source code I find that the pages from one user space to other are "copied" 102 if (vm_write) 103 ret = copy_from_user(target_kaddr,
104 lvec[*lvec_current].iov_base
105 + *lvec_offset,
106 bytes_to_copy);
107 else
108 ret = copy_to_user(lvec[*lvec_current].iov_base
109 + *lvec_offset,
110 target_kaddr, bytes_to_copy);
The code I wrote (very similar to this) also copies page contents. But my interest is transfering pages (zero-copy). Regards. PAP
> Subject: Re: transfering pages from user space to user space > From: ydroneaud@xxxxxxxxxx > To: ppessolani@xxxxxxxxxxx > Date: Thu, 6 Dec 2012 10:30:27 +0100 > CC: kernelnewbies@xxxxxxxxxxxxxxxxx > > Hi, > > Le mercredi 05 décembre 2012 à 22:47 -0300, Pablo Pessolani a écrit : > > 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. > > This sounds a lot like "Cross Memory Support" (eg CROSS_MEMORY_ATTACH > option) introduced in Linux 3.2: > > http://kernelnewbies.org/Linux_3.2#head-a5e26c6275e85a5c9c41873fbab96bd38d934b72 > > Cross Memory Support add two syscalls: > - process_vm_readv() : read from a process memory > - process_vm_writev() : write to a process memory > > Details can be found here: > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=fcf634098c00dd9cd247447368495f0b79be12d1 > > And documentation here: > > http://www.man7.org/linux/man-pages/man2/process_vm_readv.2.html > http://ozlabs.org/~cyeoh/cma/process_vm_readv.txt > > > [...] The kernel I use is 2.6.32. > > > > BTW, why use a kernel released 3 years ago for such new development ? > Kernel 2.6.32 was released the 3rd of december 2009. Even the -rt > project switch to newer kernel (eg. no less than 3.0, and up to 3.4), > see http://rt.wiki.kernel.org/ > > You should at least switch to a current long term support kernels, for > example Linux 3.4. See > http://www.kroah.com/log/linux/stable-status-08-2012.html > > Regards > > -- > Yann Droneaud > OPTEYA > > > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies |
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