On Fri, Jan 19, 2007 at 11:57:00AM +0530, Suparna Bhattacharya (suparna@xxxxxxxxxx) wrote: > > > Since you are implementing new APIs here, have you considered doing an > > > aio_sendfilev to be able to send a header with the data ? > > > > It is doable, but why people do not like corking? > > With Linux less than microsecond syscall overhead it is better and more > > flexible solution, doesn't it? > > That is what I used to think as well. However ... > > The problem as I understand it now is not about bunching data together, but > of ensuring some sort of atomicity between the header and the data, when > there can be multiple outstanding aio requests on the same socket - i.e > ensuring strict ordering without other data coming in between, when data > to be sent is not already in cache, and in the meantime another sendfile > or aio write requests comes in for the same socket. Without having to lock > the socket when reading data from disk. No, socket locking is not solution at all here. But the same applies to header - it will be copied into socket queue, then socket will be unlocked and populated VFS data will be put into that queue too, but there is a window between socket unlock after header copy and file data copy. If we will hold socket lock after header is copied, it is possible to lock it for too long - bad sectors on disk, and reading might take forever. > There are alternate ways to address this, aio_sendfilev is one of the options > I have heard people requesting. I bet those people worked with different Unix systems, which have much slower syscalls, so they combine several operations into one call. Only from this perspective I see any benefit from having header in the syscall related to file transfer. Since I already "optimized" open() syscall into file sending, things can not became worse if I will put there header pointer too. I will schedule new kevent release with this change somewhere after current work on M-on-N threading model. > Regards > Suparna -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
