On Sun, Dec 01, 2019 at 12:15:06AM +0100, Mateusz Guzik wrote:
> On 12/1/19, Konstantin Belousov <[email protected]> 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>
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