From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Sender: Tejun Heo Date: Mon, 4 Dec 2017 15:02:33 -0800 From: Tejun Heo To: Kirill Tkhai Cc: axboe@kernel.dk, bcrl@kvack.org, viro@zeniv.linux.org.uk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-aio@kvack.org, oleg@redhat.com Subject: Re: [PATCH 0/5] blkcg: Limit maximum number of aio requests available for cgroup Message-ID: <20171204230233.GQ2421075@devbig577.frc2.facebook.com> References: <151240305010.10164.15584502480037205018.stgit@localhost.localdomain> <20171204200756.GC2421075@devbig577.frc2.facebook.com> <17b22d53-ad3d-1ba8-854f-fc2a43d86c44@virtuozzo.com> <20171204215234.GN2421075@devbig577.frc2.facebook.com> <6eaa11a6-a087-42ab-df65-9142b59bf726@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <6eaa11a6-a087-42ab-df65-9142b59bf726@virtuozzo.com> List-ID: Hello, Kirill. On Tue, Dec 05, 2017 at 01:49:42AM +0300, Kirill Tkhai wrote: > > If the only reason is kernel memory consumption protection, the only > > thing we need to do is making sure that memory used for aio commands > > are accounted against cgroup kernel memory consumption and > > relaxing/removing system wide limit. > > So, we just use GFP_KERNEL_ACCOUNT flag for allocation of internal aio > structures and pages, and all the memory will be accounted in kmem and > limited by memcg. Looks very good. Yeah. > One detail about memory consumption. io_submit() calls primitives > file_operations::write_iter and read_iter. It's not clear for me whether > they consume the same memory as if writev() or readv() system calls > would be used instead. writev() may delay the actual write till dirty > pages limit will be reached, so it seems logic of the accounting should > be the same. So aio mustn't use more not accounted system memory in file > system internals, then simple writev(). > > Could you please to say if you have thoughts about this? I'm not too familiar with vfs / filesystems but I don't think there's gonna be significant unaccounted memory consumption. It shouldn't be too difficult to find out with experiments too. Thanks. -- tejun