[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH mini-os enhancements for vtpm 2/8] add posix io to blkfront
Matthew Fioravante, le Mon 17 Sep 2012 17:55:43 -0400, a écrit : > + /* Read mode checks */ > + else > + { > + /*If the requested read is bigger than the disk, just > + * read as much as we can until the end */ > + if(offset + count > disksize) { > + count = offset >= disksize ? 0 : disksize - offset; > + } > + } Perhaps return 0 here already instead of just setting count to 0? > + > + /* Setup aiocb block object */ > + aiocb.aio_dev = dev; > + aiocb.aio_nbytes = blocksize; > + aiocb.aio_offset = blknum * blocksize; > + aiocb.aio_cb = NULL; > + aiocb.data = NULL; > + > + /* If our buffer is unaligned or its aligned but we will need to rw > a partial block > + * then a copy will have to be done */ > + if(!alignedbuf || blkoff != 0 || count % blocksize != 0) { > + copybuf = _xmalloc(blocksize, dev->info.sector_size); > + } > + > + rc = count; > + while(count > 0) { > + /* determine how many bytes to read/write from/to the current > block buffer */ > + bytes = count > (blocksize - blkoff) ? blocksize - blkoff : count; Mmm. Optimizing the non-aligned case would make the code tricky, but shouldn't optimizing the aligned case at least a little bit not too hard? i.e. set bytes to max(count, BLKIF_MAX_SEGMENTS_PER_REQUEST*PAGE_SIZE); in the optimized case? That'd get much better 44KiB transfers instead of one sector at a time. Ideally we should even push a series of aio requests, but that's a lot less easy since you need to know how many requests you can afford. Apart from that, Acked-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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