From mboxrd@z Thu Jan 1 00:00:00 1970 From: keith.busch@intel.com (Keith Busch) Date: Wed, 6 Jan 2016 22:54:57 +0000 Subject: Maximum NVMe IO command size > 1MB? In-Reply-To: References: <20160106193127.GA20732@localhost.localdomain> <680a6c16f5464419b7e1974d04026951@SC-EXCH01.marvell.com> Message-ID: <20160106225457.GA23888@localhost.localdomain> On Wed, Jan 06, 2016@09:56:24PM +0000, Xuehua Chen wrote: > Hi, Keith, > > I wonder whether this could be caused by BIO_MAX_PAGES defined as 256, which means 1MB at most. > What do you think? I think you got it. You're running O_DIRECT, and fs/direct-io.c, dio_new_bio() allocates up to BIO_MAX_PAGES. I can't tell where the value for came from (looks like it was there from the very first git commit), but maybe you can propose raising it if you set BIO_MAX_PAGES higher without issue.