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On Fri, 26 Jun 1998, Chris Wedgwood wrote: > > > True, aio_* with page aligned buffers and vm hacks amount to the same > > > thing anyhow, but I don't know of anyone actively working on the mm > > > system in this area. > > > > AFAIK, there is indeed nobody working on this. If people > > actually want this feature, I'll add it to the TODO-list > > on http://linux-mm.home.ml.org/... > > People are going to give you lots of reasons why this isn't a good idea. I'm > going to say it has implication outside of networking that make it look very > attractive. > > A couple of reasons, access patterns like: > > read(from,buf,len); > write(from,buf,len); > > can be optimized to DMA to memory, twiddle some pages for the process, and > avoid the costly copy to/from buffer cache that presently limits disk IO > throughput (preserving the buffer cache using COW). > > At the moment, if I want to copy a 50MB file from one device to another, > assuming I have lots of memory, the data first gets loaded into the buffer > cache (say, via DMA), then that is copied to userspace, which then does a > write and userspace gets copied to buffer-cache, which is then written to > the destination device. > > If you follow this argument through, and make minor modifications to > userland code (such as 'cp'), you can also make this pretty click when > copying to/from NFS. This would argue for a win32 alike, but more general, copyfile() system call. This can be a very good alternative for the very expensive copies we're doing now. Since this call is in smbfs too, it means we can do a copy of a file on a samba share without the file ever traveling over the network... Rik. +-------------------------------------------------------------------+ | Linux memory management tour guide. H.H.vanRiel@phys.uu.nl | | Scouting Vries cubscout leader. http://www.phys.uu.nl/~riel/ | +-------------------------------------------------------------------+ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu | ||||||||||||
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