From: Michel Lespinasse <walken@google.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Ingo Molnar <mingo@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
Hugh Dickins <hughd@google.com>, Jorn_Engel <joern@logfs.org>,
Rik van Riel <riel@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/9] Avoid populating unbounded num of ptes with mmap_sem held
Date: Fri, 21 Dec 2012 16:59:38 -0800 [thread overview]
Message-ID: <CANN689H+yOeA3pvBMGu52q7brfoDwtkh0pA==c8VVoCkapkx6g@mail.gmail.com> (raw)
In-Reply-To: <CALCETrUi4JJSahrDKBARrwGsGE=1RbH8WL4tk1YgDmEowzXtSQ@mail.gmail.com>
On Fri, Dec 21, 2012 at 4:36 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Thu, Dec 20, 2012 at 4:49 PM, Michel Lespinasse <walken@google.com> wrote:
>> We have many vma manipulation functions that are fast in the typical case,
>> but can optionally be instructed to populate an unbounded number of ptes
>> within the region they work on:
>> - mmap with MAP_POPULATE or MAP_LOCKED flags;
>> - remap_file_pages() with MAP_NONBLOCK not set or when working on a
>> VM_LOCKED vma;
>> - mmap_region() and all its wrappers when mlock(MCL_FUTURE) is in effect;
>> - brk() when mlock(MCL_FUTURE) is in effect.
>>
>
> Something's buggy here. My evil test case is stuck with lots of
> threads spinning at 100% system time. Stack traces look like:
>
> [<0000000000000000>] __mlock_vma_pages_range+0x66/0x70
> [<0000000000000000>] __mm_populate+0xf9/0x150
> [<0000000000000000>] vm_mmap_pgoff+0x9f/0xc0
> [<0000000000000000>] sys_mmap_pgoff+0x7e/0x150
> [<0000000000000000>] sys_mmap+0x22/0x30
> [<0000000000000000>] system_call_fastpath+0x16/0x1b
> [<0000000000000000>] 0xffffffffffffffff
>
> perf top says:
>
> 38.45% [kernel] [k] __mlock_vma_pages_range
> 33.04% [kernel] [k] __get_user_pages
> 28.18% [kernel] [k] __mm_populate
>
> The tasks in question use MCL_FUTURE but not MAP_POPULATE. These
> tasks are immune to SIGKILL.
Looking into it.
There seems to be a problem with mlockall - the following program
fails in an unkillable way even before my changes:
#include <sys/mman.h>
#include <stdio.h>
#include <stdint.h>
int main(void) {
void *p = mmap(NULL, 0x100000000000,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
-1, 0);
printf("p: %p\n", p);
mlockall(MCL_CURRENT);
return 0;
}
I think my changes propagate this existing problem so it now shows up
in more places :/
--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
--
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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2012-12-22 0:59 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-21 0:49 Michel Lespinasse
2012-12-21 0:49 ` [PATCH 1/9] mm: make mlockall preserve flags other than VM_LOCKED in def_flags Michel Lespinasse
2012-12-22 4:25 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 2/9] mm: remap_file_pages() fixes Michel Lespinasse
2013-01-03 0:31 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 3/9] mm: introduce mm_populate() for populating new vmas Michel Lespinasse
2013-01-03 2:14 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 4/9] mm: use mm_populate() for blocking remap_file_pages() Michel Lespinasse
2013-01-03 2:25 ` Rik van Riel
2013-03-10 18:55 ` Tommi Rantala
2013-03-11 23:03 ` Andrew Morton
2013-03-12 0:24 ` Michel Lespinasse
2013-03-12 4:23 ` Hillf Danton
2013-03-12 5:01 ` Michel Lespinasse
2013-03-12 20:47 ` Andrew Morton
2012-12-21 0:49 ` [PATCH 5/9] mm: use mm_populate() when adjusting brk with MCL_FUTURE in effect Michel Lespinasse
2013-01-03 2:56 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 6/9] mm: use mm_populate() for mremap() of VM_LOCKED vmas Michel Lespinasse
2013-01-03 5:47 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 7/9] mm: remove flags argument to mmap_region Michel Lespinasse
2013-01-03 5:49 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 8/9] mm: directly use __mlock_vma_pages_range() in find_extend_vma() Michel Lespinasse
2013-01-03 5:50 ` Rik van Riel
2012-12-21 0:49 ` [PATCH 9/9] mm: introduce VM_POPULATE flag to better deal with racy userspace programs Michel Lespinasse
2013-01-03 6:20 ` Rik van Riel
2012-12-21 10:46 ` [PATCH 0/9] Avoid populating unbounded num of ptes with mmap_sem held Michel Lespinasse
2012-12-22 15:02 ` Greg Ungerer
2013-01-23 13:37 ` Greg Ungerer
2012-12-22 0:36 ` Andy Lutomirski
2012-12-22 0:59 ` Michel Lespinasse [this message]
2012-12-22 1:09 ` Andy Lutomirski
2012-12-22 1:59 ` Michel Lespinasse
2012-12-22 2:16 ` Andy Lutomirski
2012-12-22 9:37 ` Michel Lespinasse
2012-12-22 9:45 ` [PATCH 10/9] mm: make do_mmap_pgoff return populate as a size in bytes, not as a bool Michel Lespinasse
2013-01-03 6:21 ` Rik van Riel
2013-01-03 18:54 ` Andy Lutomirski
2013-01-03 18:56 ` [PATCH 0/9] Avoid populating unbounded num of ptes with mmap_sem held Andy Lutomirski
2013-01-04 18:16 ` Andy Lutomirski
2013-01-04 22:58 ` Michel Lespinasse
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CANN689H+yOeA3pvBMGu52q7brfoDwtkh0pA==c8VVoCkapkx6g@mail.gmail.com' \
--to=walken@google.com \
--cc=akpm@linux-foundation.org \
--cc=hughd@google.com \
--cc=joern@logfs.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=riel@redhat.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox