On Sun, 31 Oct 2004, Pat LaVarre wrote: > Alan S: > > > Why do you say the I/O isn't aligned to page boundaries? > > The memory addresses of the data buffers were not visible. > > The lengths of the commands (CDB's) were aligned: x40 blocks always. > > The addresses (LBA's) of the commands were misaligned: hex x10 blocks > off up away from zero. The retry was less aligned: hex off 8 blocks up > away from zero.
By what standard does that make them misaligned? If a page is 4096 bytes then those addresses were all page-aligned. > > We don't know where the data lies in memory. > > Agreed. > > As the flash/ CD-RW/ DVD+RW precedents of having alignment in LBA and > block length matter grow more significant, e.g., in HDD that report > more than 0.5 KiB per write, ... then we may see Linux I/O learn to > align LBA's, not just block lengths. Meanwhile, I see people write > device firmware to more or less effectively tolerate misalignment. Part of the problem resides in the filesystem design and the disk partitioning, issues which cannot be addressed solely from within the kernel. For example, if a disk partition starts at a block number that is not an even multiple of 8 (or 128, or whatever number happens to be significant) then all the files within that partition are doomed to be offset by a similar amount. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
