linux-kernel - Re: oom-killer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACDBo54KihsV=8NLGZkTghTzb2p70WURF2L5op=fW7DGj_vJ1A@mail.gmail.com>
Date:   Tue, 6 Aug 2019 20:39:22 +0530
From:   Pankaj Suryawanshi <pankajssuryawanshi@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, pankaj.suryawanshi@...fochips.com
Subject: Re: oom-killer

On Tue, Aug 6, 2019 at 8:37 PM Michal Hocko <mhocko@...nel.org> wrote:
>
> On Tue 06-08-19 20:24:03, Pankaj Suryawanshi wrote:
> > On Tue, 6 Aug, 2019, 1:46 AM Michal Hocko, <mhocko@...nel.org> wrote:
> > >
> > > On Mon 05-08-19 21:04:53, Pankaj Suryawanshi wrote:
> > > > On Mon, Aug 5, 2019 at 5:35 PM Michal Hocko <mhocko@...nel.org> wrote:
> > > > >
> > > > > On Mon 05-08-19 13:56:20, Vlastimil Babka wrote:
> > > > > > On 8/5/19 1:24 PM, Michal Hocko wrote:
> > > > > > >> [  727.954355] CPU: 0 PID: 56 Comm: kworker/u8:2 Tainted: P           O  4.14.65 #606
> > > > > > > [...]
> > > > > > >> [  728.029390] [<c034a094>] (oom_kill_process) from [<c034af24>] (out_of_memory+0x140/0x368)
> > > > > > >> [  728.037569]  r10:00000001 r9:c12169bc r8:00000041 r7:c121e680 r6:c1216588 r5:dd347d7c > [  728.045392]  r4:d5737080
> > > > > > >> [  728.047929] [<c034ade4>] (out_of_memory) from [<c03519ac>]  (__alloc_pages_nodemask+0x1178/0x124c)
> > > > > > >> [  728.056798]  r7:c141e7d0 r6:c12166a4 r5:00000000 r4:00001155
> > > > > > >> [  728.062460] [<c0350834>] (__alloc_pages_nodemask) from [<c021e9d4>] (copy_process.part.5+0x114/0x1a28)
> > > > > > >> [  728.071764]  r10:00000000 r9:dd358000 r8:00000000 r7:c1447e08 r6:c1216588 r5:00808111
> > > > > > >> [  728.079587]  r4:d1063c00
> > > > > > >> [  728.082119] [<c021e8c0>] (copy_process.part.5) from [<c0220470>] (_do_fork+0xd0/0x464)
> > > > > > >> [  728.090034]  r10:00000000 r9:00000000 r8:dd008400 r7:00000000 r6:c1216588 r5:d2d58ac0
> > > > > > >> [  728.097857]  r4:00808111
> > > > > > >
> > > > > > > The call trace tells that this is a fork (of a usermodhlper but that is
> > > > > > > not all that important.
> > > > > > > [...]
> > > > > > >> [  728.260031] DMA free:17960kB min:16384kB low:25664kB high:29760kB active_anon:3556kB inactive_anon:0kB active_file:280kB inactive_file:28kB unevictable:0kB writepending:0kB present:458752kB managed:422896kB mlocked:0kB kernel_stack:6496kB pagetables:9904kB bounce:0kB free_pcp:348kB local_pcp:0kB free_cma:0kB
> > > > > > >> [  728.287402] lowmem_reserve[]: 0 0 579 579
> > > > > > >
> > > > > > > So this is the only usable zone and you are close to the min watermark
> > > > > > > which means that your system is under a serious memory pressure but not
> > > > > > > yet under OOM for order-0 request. The situation is not great though
> > > > > >
> > > > > > Looking at lowmem_reserve above, wonder if 579 applies here? What does
> > > > > > /proc/zoneinfo say?
> > > >
> > > >
> > > > What is  lowmem_reserve[]: 0 0 579 579 ?
> > >
> > > This controls how much of memory from a lower zone you might an
> > > allocation request for a higher zone consume. E.g. __GFP_HIGHMEM is
> > > allowed to use both lowmem and highmem zones. It is preferable to use
> > > highmem zone because other requests are not allowed to use it.
> > >
> > > Please see __zone_watermark_ok for more details.
> > >
> > >
> > > > > This is GFP_KERNEL request essentially so there shouldn't be any lowmem
> > > > > reserve here, no?
> > > >
> > > >
> > > > Why only low 1G is accessible by kernel in 32-bit system ?
> >
> >
> > 1G ivirtual or physical memory (I have 2GB of RAM) ?
>
> virtual
>
 I have set 2G/2G still it works ?

>
> > > https://www.kernel.org/doc/gorman/, https://lwn.net/Articles/75174/
> > > and many more articles. In very short, the 32b virtual address space
> > > is quite small and it has to cover both the users space and the
> > > kernel. That is why we do split it into 3G reserved for userspace and 1G
> > > for kernel. Kernel can only access its 1G portion directly everything
> > > else has to be mapped explicitly (e.g. while data is copied).
> > > Thanks Michal.
> >
> >
> > >
> > > > My system configuration is :-
> > > > 3G/1G - vmsplit
> > > > vmalloc = 480M (I think vmalloc size will set your highmem ?)
> > >
> > > No, vmalloc is part of the 1GB kernel adress space.
> >
> > I read in one article , vmalloc end is fixed if you increase vmalloc
> > size it decrease highmem. ?
> > Total = lowmem + (vmalloc + high mem)
>
> As the kernel is using vmalloc area _directly_ then it has to be a part
> of the kernel address space - thus reducing the lowmem.
> --
> Michal Hocko
> SUSE Labs