From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752795AbdAZLtb (ORCPT ); Thu, 26 Jan 2017 06:49:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:44705 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752620AbdAZLt3 (ORCPT ); Thu, 26 Jan 2017 06:49:29 -0500 Date: Thu, 26 Jan 2017 12:49:25 +0100 From: Michal Hocko To: Daniel Borkmann Cc: Alexei Starovoitov , Andrew Morton , Vlastimil Babka , Mel Gorman , Johannes Weiner , linux-mm , LKML , "netdev@vger.kernel.org" , marcelo.leitner@gmail.com Subject: Re: [PATCH 0/6 v3] kvmalloc Message-ID: <20170126114925.GH6590@dhcp22.suse.cz> References: <588907AA.1020704@iogearbox.net> <20170126074354.GB8456@dhcp22.suse.cz> <5889C331.7020101@iogearbox.net> <20170126100802.GF6590@dhcp22.suse.cz> <20170126103216.GG6590@dhcp22.suse.cz> <5889D7AD.5030103@iogearbox.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5889D7AD.5030103@iogearbox.net> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 26-01-17 12:04:13, Daniel Borkmann wrote: > On 01/26/2017 11:32 AM, Michal Hocko wrote: > > On Thu 26-01-17 11:08:02, Michal Hocko wrote: > > > On Thu 26-01-17 10:36:49, Daniel Borkmann wrote: > > > > On 01/26/2017 08:43 AM, Michal Hocko wrote: > > > > > On Wed 25-01-17 21:16:42, Daniel Borkmann wrote: > > > [...] > > > > > > I assume that kvzalloc() is still the same from [1], right? If so, then > > > > > > it would unfortunately (partially) reintroduce the issue that was fixed. > > > > > > If you look above at flags, they're also passed to __vmalloc() to not > > > > > > trigger OOM in these situations I've experienced. > > > > > > > > > > Pushing __GFP_NORETRY to __vmalloc doesn't have the effect you might > > > > > think it would. It can still trigger the OOM killer becauset the flags > > > > > are no propagated all the way down to all allocations requests (e.g. > > > > > page tables). This is the same reason why GFP_NOFS is not supported in > > > > > vmalloc. > > > > > > > > Ok, good to know, is that somewhere clearly documented (like for the > > > > case with kmalloc())? > > > > > > I am afraid that we really suck on this front. I will add something. > > > > So I have folded the following to the patch 1. It is in line with > > kvmalloc and hopefully at least tell more than the current code. > > --- > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index d89034a393f2..6c1aa2c68887 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > > * Allocate enough pages to cover @size from the page level > > * allocator with @gfp_mask flags. Map them into contiguous > > * kernel virtual space, using a pagetable protection of @prot. > > + * > > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > > + * and __GFP_NOFAIL are not supported > > We could probably also mention that __GFP_ZERO in @gfp_mask is > supported, though. There are others which would be supported so I would rather stay with explicit unsupported. > > > + * Any use of gfp flags outside of GFP_KERNEL should be consulted > > + * with mm people. > > Just a question: should that read 'GFP_KERNEL | __GFP_HIGHMEM' as > that is what vmalloc() resp. vzalloc() and others pass as flags? yes, even though I think that specifying __GFP_HIGHMEM shouldn't be really necessary. Are there any users who would really insist on vmalloc pages in lowmem? Anyway this made me recheck kvmalloc_node implementation and I am not adding this flags which would mean a regression from the current state. Will fix it up. -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 0/6 v3] kvmalloc Date: Thu, 26 Jan 2017 12:49:25 +0100 Message-ID: <20170126114925.GH6590@dhcp22.suse.cz> References: <588907AA.1020704@iogearbox.net> <20170126074354.GB8456@dhcp22.suse.cz> <5889C331.7020101@iogearbox.net> <20170126100802.GF6590@dhcp22.suse.cz> <20170126103216.GG6590@dhcp22.suse.cz> <5889D7AD.5030103@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Alexei Starovoitov , Andrew Morton , Vlastimil Babka , Mel Gorman , Johannes Weiner , linux-mm , LKML , "netdev@vger.kernel.org" , marcelo.leitner@gmail.com To: Daniel Borkmann Return-path: Content-Disposition: inline In-Reply-To: <5889D7AD.5030103@iogearbox.net> Sender: owner-linux-mm@kvack.org List-Id: netdev.vger.kernel.org On Thu 26-01-17 12:04:13, Daniel Borkmann wrote: > On 01/26/2017 11:32 AM, Michal Hocko wrote: > > On Thu 26-01-17 11:08:02, Michal Hocko wrote: > > > On Thu 26-01-17 10:36:49, Daniel Borkmann wrote: > > > > On 01/26/2017 08:43 AM, Michal Hocko wrote: > > > > > On Wed 25-01-17 21:16:42, Daniel Borkmann wrote: > > > [...] > > > > > > I assume that kvzalloc() is still the same from [1], right? If so, then > > > > > > it would unfortunately (partially) reintroduce the issue that was fixed. > > > > > > If you look above at flags, they're also passed to __vmalloc() to not > > > > > > trigger OOM in these situations I've experienced. > > > > > > > > > > Pushing __GFP_NORETRY to __vmalloc doesn't have the effect you might > > > > > think it would. It can still trigger the OOM killer becauset the flags > > > > > are no propagated all the way down to all allocations requests (e.g. > > > > > page tables). This is the same reason why GFP_NOFS is not supported in > > > > > vmalloc. > > > > > > > > Ok, good to know, is that somewhere clearly documented (like for the > > > > case with kmalloc())? > > > > > > I am afraid that we really suck on this front. I will add something. > > > > So I have folded the following to the patch 1. It is in line with > > kvmalloc and hopefully at least tell more than the current code. > > --- > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index d89034a393f2..6c1aa2c68887 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > > * Allocate enough pages to cover @size from the page level > > * allocator with @gfp_mask flags. Map them into contiguous > > * kernel virtual space, using a pagetable protection of @prot. > > + * > > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > > + * and __GFP_NOFAIL are not supported > > We could probably also mention that __GFP_ZERO in @gfp_mask is > supported, though. There are others which would be supported so I would rather stay with explicit unsupported. > > > + * Any use of gfp flags outside of GFP_KERNEL should be consulted > > + * with mm people. > > Just a question: should that read 'GFP_KERNEL | __GFP_HIGHMEM' as > that is what vmalloc() resp. vzalloc() and others pass as flags? yes, even though I think that specifying __GFP_HIGHMEM shouldn't be really necessary. Are there any users who would really insist on vmalloc pages in lowmem? Anyway this made me recheck kvmalloc_node implementation and I am not adding this flags which would mean a regression from the current state. Will fix it up. -- Michal Hocko SUSE Labs -- 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