Date: Fri, 06 Sep 2013 12:14:19 -0700 From: Navdeep Parhar <nparhar@gmail.com> To: hiren panchasara <hiren.panchasara@gmail.com> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: mbuf autotuning changes Message-ID: <522A298B.30106@gmail.com> In-Reply-To: <CALCpEUFxaXKh4%2B8evratZYE3JyfyTmrL7rzpBqUJ%2B_S3Ff-AcA@mail.gmail.com> References: <CALCpEUFxaXKh4%2B8evratZYE3JyfyTmrL7rzpBqUJ%2B_S3Ff-AcA@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 09/06/13 12:10, hiren panchasara wrote:
> tunable_mbinit() in kern_mbuf.c looks like this:
>
> 119 /*
> 120 * The default limit for all mbuf related memory is 1/2 of all
> 121 * available kernel memory (physical or kmem).
> 122 * At most it can be 3/4 of available kernel memory.
> 123 */
> 124 realmem = qmin((quad_t)physmem * PAGE_SIZE,
> 125 vm_map_max(kmem_map) - vm_map_min(kmem_map));
> 126 maxmbufmem = realmem / 2;
> 127 TUNABLE_QUAD_FETCH("kern.ipc.maxmbufmem", &maxmbufmem);
> 128 if (maxmbufmem > realmem / 4 * 3)
> 129 maxmbufmem = realmem / 4 * 3;
>
> If I am reading the code correctly, we loose the value on line 126 when we
> do FETCH on line 127.
>
> And after line 127, if we havent specified kern.ipc.maxmbufmem (in
> loader.conf - I guess...), we set that value to 0.
>
> And because of that the if condition on line 128 is almost always false?
>
> What am I missing here?
All the TUNABLE_FOO_FETCH leave the data alone if the tunable isn't
actually in the environment. For this specific case, see the the
implementation of getenv_quad().
Navdeep
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?522A298B.30106>