From mboxrd@z Thu Jan 1 00:00:00 1970 From: keith.busch@linux.intel.com (Keith Busch) Date: Wed, 20 Jun 2018 16:30:35 -0600 Subject: [PATCH] nvme: use __GFP_NOWARN for iod allocation In-Reply-To: <34e64832-c345-3a70-401f-1915b5bb4af1@kernel.dk> References: <4cb394ca-7032-ea67-5bb1-ef331e42ace2@kernel.dk> <20180620204310.GA24840@localhost.localdomain> <34e64832-c345-3a70-401f-1915b5bb4af1@kernel.dk> Message-ID: <20180620223035.GA25196@localhost.localdomain> On Wed, Jun 20, 2018@02:54:26PM -0600, Jens Axboe wrote: > I should also mention that this came out of a real life hang > on a production box. I suppose we haven't seen a lot of these > since a lot of nvme controllers have a hw limit of 128k, but > the ones that don't can pretty easily hit the hang of needing > 2^2 pages and failing miserably forever. I can certainly believe that. I'm totally fine with setting a smaller upper bound on the IO size. There really isn't a meaningful bandwidth advantage to larger transfers on NVMe PCIe once you get over 256k anyway. Since you're making the change to core, let's wait to hear if there are any concerns on the fabrics front.