From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [RFC v3 0/4] vfs: Non-blockling buffered fs read (page cache only) Date: Thu, 25 Sep 2014 13:16:55 +0200 Message-ID: <20140925111655.GA8169@quack.suse.cz> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: owner-linux-aio@kvack.org To: Michael Kerrisk Cc: Milosz Tanski , Linux Kernel , Christoph Hellwig , Linux-Fsdevel , linux-aio , Mel Gorman , Volker Lendecke , Tejun Heo , Jeff Moyer , Theodore Ts'o , Al Viro , Linux API List-Id: linux-api@vger.kernel.org On Thu 25-09-14 06:06:14, Michael Kerrisk wrote: > Hello Milosz, > > On Wed, Sep 24, 2014 at 11:46 PM, Milosz Tanski wrote: > > This patcheset introduces an ability to perform a non-blocking read from > > regular files in buffered IO mode. This works by only for those filesystems > > that have data in the page cache. > > > > It does this by introducing new syscalls new syscalls preadv2/pwritev2. These > > new syscalls behave like the network sendmsg, recvmsg syscalls that accept an > > extra flag argument (RWF_NONBLOCK). > > > > It's a very common patern today (samba, libuv, etc..) use a large threadpool to > > perform buffered IO operations. They submit the work form another thread > > that performs network IO and epoll or other threads that perform CPU work. This > > leads to increased latency for processing, esp. in the case of data that's > > already cached in the page cache. > > > > With the new interface the applications will now be able to fetch the data in > > their network / cpu bound thread(s) and only defer to a threadpool if it's not > > there. In our own application (VLDB) we've observed a decrease in latency for > > "fast" request by avoiding unnecessary queuing and having to swap out current > > tasks in IO bound work threads. > > Since this is a change to the user-space API, could you CC future > versions of this patch set to linux-api@vgerr.kernel.org please, as There's typo in the address. It should be: linux-api@vger.kernel.org Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: aart@kvack.org