From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [PATCH][RFC] add MAP_UNLOCKED mmap flag Date: Tue, 6 Oct 2009 21:10:35 +0900 Message-ID: <2f11576a0910060510y401c1d5ax6f17135478d22899@mail.gmail.com> References: <20091006190938.126F.A69D9226@jp.fujitsu.com> <20091006102136.GH9832@redhat.com> <20091006192454.1272.A69D9226@jp.fujitsu.com> <20091006103300.GI9832@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: In-Reply-To: <20091006103300.GI9832@redhat.com> Sender: owner-linux-mm@kvack.org To: Gleb Natapov Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org List-Id: linux-api@vger.kernel.org 2009/10/6 Gleb Natapov : > On Tue, Oct 06, 2009 at 07:27:56PM +0900, KOSAKI Motohiro wrote: >> > On Tue, Oct 06, 2009 at 07:11:06PM +0900, KOSAKI Motohiro wrote: >> > > Hi >> > > >> > > > If application does mlockall(MCL_FUTURE) it is no longer possible to >> > > > mmap file bigger than main memory or allocate big area of anonymous >> > > > memory. Sometimes it is desirable to lock everything related to program >> > > > execution into memory, but still be able to mmap big file or allocate >> > > > huge amount of memory and allow OS to swap them on demand. MAP_UNLOCKED >> > > > allows to do that. >> > > > >> > > > Signed-off-by: Gleb Natapov >> > > >> > > Why don't you use explicit munlock()? >> > Because mmap will fail before I'll have a chance to run munlock on it. >> > Actually when I run my process inside memory limited container host dies >> > (I suppose trashing, but haven't checked). >> > >> > > Plus, Can you please elabrate which workload nedd this feature? >> > > >> > I wanted to run kvm with qemu process locked in memory, but guest memory >> > unlocked. And guest memory is bigger then host memory in the case I am >> > testing. I found out that it is impossible currently. >> >> 1. process creation (qemu) >> 2. load all library > Can't control this if program has plugging. Not qemu case > though. > >> 3. mlockall(MCL_CURRENT) >> 4. load guest OS > And what about all other allocations qemu does during its life time? Not > all of them will be small enough to be from brk area. > >> is impossible? why? >> > Because what you are proposing is not the same as mlockall(MCL_CURRENT|MCL_FUTURE); > > You essentially say that MCL_FUTURE is not needed. No, I only think your case doesn't fit MC_FUTURE. I haven't find any real benefit in this patch. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org