svn commit: r355227 - head/sys/fs/tmpfs

[Konstantin Belousov]

On Sun, Dec 01, 2019 at 12:15:06AM +0100, Mateusz Guzik wrote:
> On 12/1/19, Konstantin Belousov <kostikbel at gmail.com> wrote:
> > On Sat, Nov 30, 2019 at 04:41:48PM +0000, Mateusz Guzik wrote:
> >> Author: mjg
> >> Date: Sat Nov 30 16:41:47 2019
> >> New Revision: 355227
> >> URL: https://svnweb.freebsd.org/changeset/base/355227
> >>
> >> Log:
> >>   tmpfs: add fast path to tmpfs_access for common case lookup
> >>
> >>   VEXEC consists of vast majority of all calls and almost all targets
> >> have
> >>   at least 0111.
> > On what load VEXEC is the dominant access check ?
> >
> 
> Note this is called for every directory to be traversed dooring lookup,
> so for instance looking up "foo/bar/baz" performs 2 VEXEC checks.
So it is for directory components traversal during lookup.
Does it make sense to add something similar at the start of
ufs_accessx() when neither kind of ACLs is enabled for mp ?

> 
> Sample result from buildkernel. 64 is VEXEC.
> 
> dtrace -n 'fbt::tmpfs_access:entry { @[args[0]->a_accmode, ((struct
> tmpfs_node *)args[0]->a_vp->v_data)->tn_mode & 0111] = count(); }'
> dtrace: description 'fbt::tmpfs_access:entry ' matched 1 probe
> 
> 
>       384       73                1
>     16512        0                2
>       128        0               68
>       384        0              877
>      4096        0             1049
>       320       73             5965
>      4096       73            32471
>       128       73           145115
>       256       73           160569
>       256        0           999827
>        64       73         32320731
> 
> >>
> >> Modified:
> >>   head/sys/fs/tmpfs/tmpfs_vnops.c
> >>
> >> Modified: head/sys/fs/tmpfs/tmpfs_vnops.c
> >> ==============================================================================
> >> --- head/sys/fs/tmpfs/tmpfs_vnops.c	Sat Nov 30 16:40:16 2019	(r355226)
> >> +++ head/sys/fs/tmpfs/tmpfs_vnops.c	Sat Nov 30 16:41:47 2019	(r355227)
> >> @@ -331,6 +331,12 @@ tmpfs_access(struct vop_access_args *v)
> >>
> >>  	node = VP_TO_TMPFS_NODE(vp);
> >>
> >> +	/*
> >> +	 * Common case path lookup.
> >> +	 */
> >> +	if (__predict_true(accmode == VEXEC && (node->tn_mode & 0111) == 0111))
> > The 0111 must be spelled as (S_IXUSR | S_IXGRP | S_IXOTH).
> >
> 
> Ok.
> 
> >> +		return (0);
> >> +
> >>  	switch (vp->v_type) {
> >>  	case VDIR:
> >>  		/* FALLTHROUGH */
> >
> 
> 
> -- 
> Mateusz Guzik <mjguzik gmail.com>