On Wednesday February 6, wd@xxxxxxx wrote: > > We implemented the option to select kernel page sizes of 4, 16, 64 > and 256 kB for some PowerPC systems (440SPe, to be precise). A nice > graphics of the effect can be found here: > > https://www.amcc.com/MyAMCC/retrieveDocument/PowerPC/440SPe/RAIDinLinux_PB_0529a.pdf Thanks for the link! <quote> The second improvement is to remove a memory copy that is internal to the MD driver. The MD driver stages strip data ready to be written next to the I/O controller in a page size pre- allocated buffer. It is possible to bypass this memory copy for sequential writes thereby saving SDRAM access cycles. </quote> I sure hope you've checked that the filesystem never (ever) changes a buffer while it is being written out. Otherwise the data written to disk might be different from the data used in the parity calculation :-) And what are the "Second memcpy" and "First memcpy" in the graph? I assume one is the memcpy mentioned above, but what is the other? NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
