From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kirill A. Shutemov" Subject: Re: [PATCH V4 5/6] mm: mmap: Add mmap flag to request VM_LOCKONFAULT Date: Wed, 22 Jul 2015 18:45:29 +0300 Message-ID: <20150722154529.GA9107@node.dhcp.inet.fi> References: <1437508781-28655-1-git-send-email-emunson@akamai.com> <1437508781-28655-6-git-send-email-emunson@akamai.com> <20150722112558.GC8630@node.dhcp.inet.fi> <20150722143220.GB3203@akamai.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150722143220.GB3203@akamai.com> Sender: linux-arch-owner@vger.kernel.org To: Eric B Munson Cc: Andrew Morton , Michal Hocko , Vlastimil Babka , Paul Gortmaker , Chris Metcalf , Guenter Roeck , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org List-Id: linux-api@vger.kernel.org On Wed, Jul 22, 2015 at 10:32:20AM -0400, Eric B Munson wrote: > On Wed, 22 Jul 2015, Kirill A. Shutemov wrote: > > > On Tue, Jul 21, 2015 at 03:59:40PM -0400, Eric B Munson wrote: > > > The cost of faulting in all memory to be locked can be very high when > > > working with large mappings. If only portions of the mapping will be > > > used this can incur a high penalty for locking. > > > > > > Now that we have the new VMA flag for the locked but not present state, > > > expose it as an mmap option like MAP_LOCKED -> VM_LOCKED. > > > > What is advantage over mmap() + mlock(MLOCK_ONFAULT)? > > There isn't one, it was added to maintain parity with the > mlock(MLOCK_LOCK) -> mmap(MAP_LOCKED) set. I think not having will lead > to confusion because we have MAP_LOCKED so why don't we support > LOCKONFAULT from mmap as well. I don't think it's ia good idea to spend bits in flags unless we have a reason for that. BTW, you have typo on sparc: s/0x8000/0x80000/. -- Kirill A. Shutemov