Date: Mon, 23 Jun 2014 14:00:37 +0400 From: Dmitry Sivachenko <trtrmitya@gmail.com> To: hackers@freebsd.org Subject: Re: mlock() and vm_max_wired Message-ID: <C187B4D5-7D29-426F-BF90-06CFB023B702@gmail.com> In-Reply-To: <D85BD1F5-414C-45FA-B509-C55DC9BE125A@gmail.com> References: <D85BD1F5-414C-45FA-B509-C55DC9BE125A@gmail.com>
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On 23 =D0=B8=D1=8E=D0=BD=D1=8F 2014 =D0=B3., at 13:52, Dmitry Sivachenko =
<trtrmitya@gmail.com> wrote:
> Hello!
>=20
> I am using FreeBSD-10/stable and have a problem with mlock().
> I have 256GB of memory and a program which does mmap+mlock on a number =
of data files. It can process one file several times (so it does mmap() =
+ mlock() on the same file more than once).
> I set vm.max_wired=3D67108864 (67108864 * 4k =3D 256GB), so it is =
allowed to mlock() the whole RAM.
>=20
> The total size of all files is about 180GB.
>=20
> The program fails with mlock: Resource temporarily unavailable error.
>=20
> If I increase vm.max_wired even more, the program works fine and after =
it starts top(1) shows about 186GB of Wired memory.
>=20
> Why does it fail with vm.max_wired=3D67108864? Is it a bug or am I =
missing something?
>=20
> Thanks.
Forgot to add the I suspect the following fragment in vm_mmap.c, in =
vm_mlock() function:
if (npages + cnt.v_wire_count > vm_page_max_wired)
return (EAGAIN);
If we mlock() the same region second time, this condition can be true =
though after mlock() these pages will not increase total locked pages =
counter.=
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