Fajun Chen wrote:
.. I verified your program works in my system and my application works as well if changed accordingly. However, this change (indirect IO in sg term) may come at a performance cost for IO intensive applications since it does NOT utilize mmaped buffer managed by sg driver. Please see relevant sg document below: http://sg.torque.net/sg/p/sg_v3_ho.html#id2495330 http://sg.torque.net/sg/p/sg_v3_ho.html#dmmio As an example, sg_rbuf.c in sg3_util package uses SG_FLAG_MMAP_IO flag in SG_IO. Please see source code attached. I also noticed that MAP_ANONYMOUS is NOT used in mmap() call in sg_rbuf.c, which may not be desirable as you pointed out in previous emails. So this brings up an interesting sg usage issue: can we use MAP_ANONYMOUS with SG_FLAG_MMAP_IO flag in SG_IO?
.. The SG_FLAG_MMAP works only with /dev/sg* devices, not /dev/sd* devices. I don't know which kind you were trying to use, since you still have not provided your source code for examination. If you are using /dev/sg*, then you should be able to get your original mmap() code to work. But the behaviour described thus far seems to indicate that your secret program must have been using /dev/sd* instead. Cheers - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
