lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 19 Jan 2007 12:23:43 +0300 From: Evgeniy Polyakov <johnpol@....mipt.ru> To: Suparna Bhattacharya <suparna@...ibm.com> Cc: David Miller <davem@...emloft.net>, Ulrich Drepper <drepper@...hat.com>, Andrew Morton <akpm@...l.org>, netdev <netdev@...r.kernel.org>, Zach Brown <zach.brown@...cle.com>, Christoph Hellwig <hch@...radead.org>, Chase Venters <chase.venters@...entec.com>, Johann Borck <johann.borck@...sedata.com>, linux-kernel@...r.kernel.org, Jeff Garzik <jeff@...zik.org>, Jamal Hadi Salim <hadi@...erus.ca>, Ingo Molnar <mingo@...e.hu>, linux-fsdevel@...r.kernel.org Subject: Re: [take33 10/10] kevent: Kevent based AIO (aio_sendfile()/aio_sendfile_path()). On Fri, Jan 19, 2007 at 11:57:00AM +0530, Suparna Bhattacharya (suparna@...ibm.com) 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 netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists