High rate of NFS cache misses after upgrading from 10.3-prerelease to 11.1-release

[Niels Kobschaetzki]

On 04/14/2018 03:49 AM, Rick Macklem wrote:

> If you go into ncl_getattrcache() {it's in sys/fs/nfsclient/nfs_clsubs.c}
> and add a printf() for "time_second" and "np->n_mtime.tv_sec" near the
> top, where it calculates "timeo" from it.
> Running this hacked kernel might show you if either of these fields is bogus.
> (You could then printf() "timeo" and "np->n_attrtimeo" just before the "if"
> clause that increments "attrcache_misses", which is where the cache misses
> happen to see why it is missing the cache.)
> If you could do this for the 10.3 kernel as well, this might indicate why the
> miss rate has increased?

I just checked the code to see if I can figure out where exactly I have
to put the printf(). And then I saw that there are ifdefs for
NFS_ACDEBUG which seems to be a kernel option. When I add NFS_ACDEBUG in
the config-file for the kernel, the build fails with an

/usr/src/sys/amd64/conf/ACDEBUG: unknown option "NFS_ACDEBUG"

I looked in sysctl.h and there it isn't defined. Do I do something wrong
or did this sysctl-tunable got lost at some point in time?
Can I just use this code by removing the ifdef for getting information?

Sorry, my C is not really existent, thus I have to ask :/

The parts (except the part that looks at the sysctl looks like this):
#ifdef NFS_ACDEBUG
        if (nfs_acdebug>1)
                printf("ncl_getattrcache: initial timeo = %d\n", timeo);
#endif

……


#ifdef NFS_ACDEBUG
        if (nfs_acdebug > 2)
                printf("acregmin %d; acregmax %d; acdirmin %d; acdirmax
%d\n",
                    nmp->nm_acregmin, nmp->nm_acregmax,
                    nmp->nm_acdirmin, nmp->nm_acdirmax);

        if (nfs_acdebug)
                printf("ncl_getattrcache: age = %d; final timeo = %d\n",
                    (time_second - np->n_attrstamp), timeo);
#endif


I would remove the ifdefs and the "if (nfs_acdebug …)"

Niels