kernel/auditsc.c | 39 +++++++++++++++++---------------------- 1 file changed, 17 insertions(+), 22 deletions(-)
Whenever there's audit context, __audit_inode_child() gets called
numerous times, which can lead to high latency in scenarios that
create too many sysfs/debugfs entries at once, for instance, upon
device_add_disk() invocation.
# uname -r
6.17.0-rc3+
# auditctl -a always,exit -F path=/tmp -k foo
# time insmod loop max_loop=1000
real 0m42.753s
user 0m0.000s
sys 0m42.494s
# perf record -a insmod loop max_loop=1000
# perf report --stdio |grep __audit_inode_child
37.95% insmod [kernel.kallsyms] [k] __audit_inode_child
__audit_inode_child() searches for both the parent and the child
in two different loops that iterate over the same list. This
process can be optimized by merging these into a single loop,
without changing the function behavior or affecting the code's
readability.
This patch merges the two loops that walk through the list
context->names_list into a single loop. This optimization resulted
in around 54% performance enhancement for the benchmark.
# uname -r
6.17.0-rc3+-enhanced
# auditctl -a always,exit -F path=/tmp -k foo
# time insmod loop max_loop=1000
real 0m19.388s
user 0m0.000s
sys 0m19.149s
Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
---
kernel/auditsc.c | 39 +++++++++++++++++----------------------
1 file changed, 17 insertions(+), 22 deletions(-)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index d1966144bdfe..8cebc016d9eb 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2416,41 +2416,36 @@ void __audit_inode_child(struct inode *parent,
if (inode)
handle_one(inode);
- /* look for a parent entry first */
list_for_each_entry(n, &context->names_list, list) {
- if (!n->name ||
- (n->type != AUDIT_TYPE_PARENT &&
- n->type != AUDIT_TYPE_UNKNOWN))
+ /* can only match entries that have a name */
+ if (!n->name)
continue;
- if (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&
- !audit_compare_dname_path(dname,
- n->name->name, n->name_len)) {
+ /* look for a parent entry first */
+ if (!found_parent &&
+ (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&
+ !audit_compare_dname_path(dname, n->name->name, n->name_len))) {
if (n->type == AUDIT_TYPE_UNKNOWN)
n->type = AUDIT_TYPE_PARENT;
found_parent = n;
- break;
- }
- }
-
- cond_resched();
-
- /* is there a matching child entry? */
- list_for_each_entry(n, &context->names_list, list) {
- /* can only match entries that have a name */
- if (!n->name ||
- (n->type != type && n->type != AUDIT_TYPE_UNKNOWN))
+ if (found_child)
+ break;
continue;
+ }
- if (!strcmp(dname->name, n->name->name) ||
- !audit_compare_dname_path(dname, n->name->name,
+ /* is there a matching child entry? */
+ if (!found_child &&
+ (n->type == type || n->type == AUDIT_TYPE_UNKNOWN) &&
+ (!strcmp(dname->name, n->name->name) ||
+ !audit_compare_dname_path(dname, n->name->name,
found_parent ?
found_parent->name_len :
- AUDIT_NAME_FULL)) {
+ AUDIT_NAME_FULL))) {
if (n->type == AUDIT_TYPE_UNKNOWN)
n->type = type;
found_child = n;
- break;
+ if (found_parent)
+ break;
}
}
--
2.51.0On Oct 22, 2025 Ricardo Robaina <rrobaina@redhat.com> wrote:
>
> Whenever there's audit context, __audit_inode_child() gets called
> numerous times, which can lead to high latency in scenarios that
> create too many sysfs/debugfs entries at once, for instance, upon
> device_add_disk() invocation.
>
> # uname -r
> 6.17.0-rc3+
>
> # auditctl -a always,exit -F path=/tmp -k foo
> # time insmod loop max_loop=1000
> real 0m42.753s
> user 0m0.000s
> sys 0m42.494s
>
> # perf record -a insmod loop max_loop=1000
> # perf report --stdio |grep __audit_inode_child
> 37.95% insmod [kernel.kallsyms] [k] __audit_inode_child
>
> __audit_inode_child() searches for both the parent and the child
> in two different loops that iterate over the same list. This
> process can be optimized by merging these into a single loop,
> without changing the function behavior or affecting the code's
> readability.
>
> This patch merges the two loops that walk through the list
> context->names_list into a single loop. This optimization resulted
> in around 54% performance enhancement for the benchmark.
>
> # uname -r
> 6.17.0-rc3+-enhanced
>
> # auditctl -a always,exit -F path=/tmp -k foo
> # time insmod loop max_loop=1000
> real 0m19.388s
> user 0m0.000s
> sys 0m19.149s
>
> Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
> ---
> kernel/auditsc.c | 39 +++++++++++++++++----------------------
> 1 file changed, 17 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index d1966144bdfe..8cebc016d9eb 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2416,41 +2416,36 @@ void __audit_inode_child(struct inode *parent,
> if (inode)
> handle_one(inode);
>
> - /* look for a parent entry first */
> list_for_each_entry(n, &context->names_list, list) {
> - if (!n->name ||
> - (n->type != AUDIT_TYPE_PARENT &&
> - n->type != AUDIT_TYPE_UNKNOWN))
> + /* can only match entries that have a name */
> + if (!n->name)
> continue;
>
> - if (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&
> - !audit_compare_dname_path(dname,
> - n->name->name, n->name_len)) {
> + /* look for a parent entry first */
> + if (!found_parent &&
> + (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&
> + !audit_compare_dname_path(dname, n->name->name, n->name_len))) {
> if (n->type == AUDIT_TYPE_UNKNOWN)
> n->type = AUDIT_TYPE_PARENT;
As mentioned in my feedback on your v1 patch, we can probably set
n->type equal to AUDIT_TYPE_PARENT without checking n->type first
as it we want this set to AUDIT_TYPE_PARENT regardless.
Please either fix this, or explain why it needs to be the way that it
is in your v2 patch.
> found_parent = n;
> - break;
> - }
> - }
> -
> - cond_resched();
> -
> - /* is there a matching child entry? */
> - list_for_each_entry(n, &context->names_list, list) {
> - /* can only match entries that have a name */
> - if (!n->name ||
> - (n->type != type && n->type != AUDIT_TYPE_UNKNOWN))
> + if (found_child)
> + break;
> continue;
> + }
>
> - if (!strcmp(dname->name, n->name->name) ||
> - !audit_compare_dname_path(dname, n->name->name,
> + /* is there a matching child entry? */
> + if (!found_child &&
> + (n->type == type || n->type == AUDIT_TYPE_UNKNOWN) &&
> + (!strcmp(dname->name, n->name->name) ||
> + !audit_compare_dname_path(dname, n->name->name,
> found_parent ?
> found_parent->name_len :
> - AUDIT_NAME_FULL)) {
> + AUDIT_NAME_FULL))) {
> if (n->type == AUDIT_TYPE_UNKNOWN)
> n->type = type;
> found_child = n;
> - break;
> + if (found_parent)
> + break;
> }
> }
>
> --
> 2.51.0
--
paul-moore.com
On Thu, Oct 23, 2025 at 3:41 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Oct 22, 2025 Ricardo Robaina <rrobaina@redhat.com> wrote:
> >
> > Whenever there's audit context, __audit_inode_child() gets called
> > numerous times, which can lead to high latency in scenarios that
> > create too many sysfs/debugfs entries at once, for instance, upon
> > device_add_disk() invocation.
> >
> > # uname -r
> > 6.17.0-rc3+
> >
> > # auditctl -a always,exit -F path=/tmp -k foo
> > # time insmod loop max_loop=1000
> > real 0m42.753s
> > user 0m0.000s
> > sys 0m42.494s
> >
> > # perf record -a insmod loop max_loop=1000
> > # perf report --stdio |grep __audit_inode_child
> > 37.95% insmod [kernel.kallsyms] [k] __audit_inode_child
> >
> > __audit_inode_child() searches for both the parent and the child
> > in two different loops that iterate over the same list. This
> > process can be optimized by merging these into a single loop,
> > without changing the function behavior or affecting the code's
> > readability.
> >
> > This patch merges the two loops that walk through the list
> > context->names_list into a single loop. This optimization resulted
> > in around 54% performance enhancement for the benchmark.
> >
> > # uname -r
> > 6.17.0-rc3+-enhanced
> >
> > # auditctl -a always,exit -F path=/tmp -k foo
> > # time insmod loop max_loop=1000
> > real 0m19.388s
> > user 0m0.000s
> > sys 0m19.149s
> >
> > Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
> > ---
> > kernel/auditsc.c | 39 +++++++++++++++++----------------------
> > 1 file changed, 17 insertions(+), 22 deletions(-)
> >
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index d1966144bdfe..8cebc016d9eb 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -2416,41 +2416,36 @@ void __audit_inode_child(struct inode *parent,
> > if (inode)
> > handle_one(inode);
> >
> > - /* look for a parent entry first */
> > list_for_each_entry(n, &context->names_list, list) {
> > - if (!n->name ||
> > - (n->type != AUDIT_TYPE_PARENT &&
> > - n->type != AUDIT_TYPE_UNKNOWN))
> > + /* can only match entries that have a name */
> > + if (!n->name)
> > continue;
> >
> > - if (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&
> > - !audit_compare_dname_path(dname,
> > - n->name->name, n->name_len)) {
> > + /* look for a parent entry first */
> > + if (!found_parent &&
> > + (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&
> > + !audit_compare_dname_path(dname, n->name->name, n->name_len))) {
> > if (n->type == AUDIT_TYPE_UNKNOWN)
> > n->type = AUDIT_TYPE_PARENT;
>
> As mentioned in my feedback on your v1 patch, we can probably set
> n->type equal to AUDIT_TYPE_PARENT without checking n->type first
> as it we want this set to AUDIT_TYPE_PARENT regardless.
>
> Please either fix this, or explain why it needs to be the way that it
> is in your v2 patch.
>
> > found_parent = n;
> > - break;
> > - }
> > - }
> > -
> > - cond_resched();
> > -
> > - /* is there a matching child entry? */
> > - list_for_each_entry(n, &context->names_list, list) {
> > - /* can only match entries that have a name */
> > - if (!n->name ||
> > - (n->type != type && n->type != AUDIT_TYPE_UNKNOWN))
> > + if (found_child)
> > + break;
> > continue;
> > + }
> >
> > - if (!strcmp(dname->name, n->name->name) ||
> > - !audit_compare_dname_path(dname, n->name->name,
> > + /* is there a matching child entry? */
> > + if (!found_child &&
> > + (n->type == type || n->type == AUDIT_TYPE_UNKNOWN) &&
> > + (!strcmp(dname->name, n->name->name) ||
> > + !audit_compare_dname_path(dname, n->name->name,
> > found_parent ?
> > found_parent->name_len :
> > - AUDIT_NAME_FULL)) {
> > + AUDIT_NAME_FULL))) {
> > if (n->type == AUDIT_TYPE_UNKNOWN)
> > n->type = type;
> > found_child = n;
> > - break;
> > + if (found_parent)
> > + break;
> > }
> > }
> >
> > --
> > 2.51.0
>
> --
> paul-moore.com
>
Hi Paul,
Thanks for the heads-up!
Now I realize I misunderstood that piece of your review the first time
I read it. I'll fix it and post a newer version of this patch shortly.
On Wed, Oct 22, 2025 at 8:36 AM Ricardo Robaina <rrobaina@redhat.com> wrote: > > Whenever there's audit context, __audit_inode_child() gets called > numerous times, which can lead to high latency in scenarios that > create too many sysfs/debugfs entries at once, for instance, upon > device_add_disk() invocation. > > # uname -r > 6.17.0-rc3+ > > # auditctl -a always,exit -F path=/tmp -k foo > # time insmod loop max_loop=1000 > real 0m42.753s > user 0m0.000s > sys 0m42.494s > > # perf record -a insmod loop max_loop=1000 > # perf report --stdio |grep __audit_inode_child > 37.95% insmod [kernel.kallsyms] [k] __audit_inode_child > > __audit_inode_child() searches for both the parent and the child > in two different loops that iterate over the same list. This > process can be optimized by merging these into a single loop, > without changing the function behavior or affecting the code's > readability. > > This patch merges the two loops that walk through the list > context->names_list into a single loop. This optimization resulted > in around 54% performance enhancement for the benchmark. > > # uname -r > 6.17.0-rc3+-enhanced > > # auditctl -a always,exit -F path=/tmp -k foo > # time insmod loop max_loop=1000 > real 0m19.388s > user 0m0.000s > sys 0m19.149s I couldn't help but notice that these numbers look *exactly* the same as the v1 patch numbers ... ;) Assuming the rest of the patch looks okay (I suspect it will), there is no need to re-spin the patch, but if there are different numbers you want me to use I can update the commit description when I merge the patch. > Signed-off-by: Ricardo Robaina <rrobaina@redhat.com> > --- > kernel/auditsc.c | 39 +++++++++++++++++---------------------- > 1 file changed, 17 insertions(+), 22 deletions(-) -- paul-moore.com
On Wed, Oct 22, 2025 at 8:51 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Wed, Oct 22, 2025 at 8:36 AM Ricardo Robaina <rrobaina@redhat.com> wrote:
> >
> > Whenever there's audit context, __audit_inode_child() gets called
> > numerous times, which can lead to high latency in scenarios that
> > create too many sysfs/debugfs entries at once, for instance, upon
> > device_add_disk() invocation.
> >
> > # uname -r
> > 6.17.0-rc3+
> >
> > # auditctl -a always,exit -F path=/tmp -k foo
> > # time insmod loop max_loop=1000
> > real 0m42.753s
> > user 0m0.000s
> > sys 0m42.494s
> >
> > # perf record -a insmod loop max_loop=1000
> > # perf report --stdio |grep __audit_inode_child
> > 37.95% insmod [kernel.kallsyms] [k] __audit_inode_child
> >
> > __audit_inode_child() searches for both the parent and the child
> > in two different loops that iterate over the same list. This
> > process can be optimized by merging these into a single loop,
> > without changing the function behavior or affecting the code's
> > readability.
> >
> > This patch merges the two loops that walk through the list
> > context->names_list into a single loop. This optimization resulted
> > in around 54% performance enhancement for the benchmark.
> >
> > # uname -r
> > 6.17.0-rc3+-enhanced
> >
> > # auditctl -a always,exit -F path=/tmp -k foo
> > # time insmod loop max_loop=1000
> > real 0m19.388s
> > user 0m0.000s
> > sys 0m19.149s
>
> I couldn't help but notice that these numbers look *exactly* the same
> as the v1 patch numbers ... ;)
>
> Assuming the rest of the patch looks okay (I suspect it will), there
> is no need to re-spin the patch, but if there are different numbers
> you want me to use I can update the commit description when I merge
> the patch.
>
> > Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
> > ---
> > kernel/auditsc.c | 39 +++++++++++++++++----------------------
> > 1 file changed, 17 insertions(+), 22 deletions(-)
>
> --
> paul-moore.com
>
Hi Paul,
I did test and collected fresh data on kernel-6.18 before posting the
v2. However, I completely forgot updating the commit message, I'm
sorry for that.
Please update it as follows:
Whenever there's audit context, __audit_inode_child() gets called
numerous times, which can lead to high latency in scenarios that
create too many sysfs/debugfs entries at once, for instance, upon
device_add_disk() invocation.
# uname -r
6.18.0-rc2+
# auditctl -a always,exit -F path=/tmp -k foo
# time insmod loop max_loop=1000
real 0m46.676s
user 0m0.000s
sys 0m46.405s
# perf record -a insmod loop max_loop=1000
# perf report --stdio |grep __audit_inode_child
32.73% insmod [kernel.kallsyms] [k]
__audit_inode_child
__audit_inode_child() searches for both the parent and the child
in two different loops that iterate over the same list. This
process can be optimized by merging these into a single loop,
without changing the function behavior or affecting the code's
readability.
This patch merges the two loops that walk through the list
context->names_list into a single loop. This optimization resulted
in around 51% performance enhancement for the benchmark.
# uname -r
6.18.0-rc2-enhanced
# auditctl -a always,exit -F path=/tmp -k foo
# time insmod loop max_loop=1000
real 0m22.991s
user 0m0.000s
sys 0m22.737s
Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
Data:
root@fedora:/home/rrobaina# uname -r
6.18.0-rc2+
root@fedora:/home/rrobaina# rmmod loop
root@fedora:/home/rrobaina# time insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
real 0m45.264s
user 0m0.001s
sys 0m44.990s
root@fedora:/home/rrobaina# rmmod loop
root@fedora:/home/rrobaina# time insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
real 0m47.383s
user 0m0.000s
sys 0m47.113s
root@fedora:/home/rrobaina# auditctl -a always,exit -F path=/tmp -k foo
root@fedora:/home/rrobaina# time insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
real 0m46.984s
user 0m0.001s
sys 0m46.679s
Average:
real 0m46.676s
user 0m0.000s
sys 0m46.405s
root@fedora:/home/rrobaina# perf record -a insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
root@fedora:/home/rrobaina# perf report --stdio |grep __audit_inode_child
32.73% insmod [kernel.kallsyms] [k]
__audit_inode_child
0.00% (udev-worker) [kernel.kallsyms] [k]
__audit_inode_child
--
root@fedora:/home/rrobaina# uname -r
6.18.0-rc2-enhanced
root@fedora:/home/rrobaina# auditctl -a always,exit -F path=/tmp -k foo
root@fedora:/home/rrobaina# rmmod loop
root@fedora:/home/rrobaina# time insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
real 0m22.793s
user 0m0.000s
sys 0m22.517s
root@fedora:/home/rrobaina# rmmod loop
root@fedora:/home/rrobaina# time insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
real 0m22.763s
user 0m0.001s
sys 0m22.524s
root@fedora:/home/rrobaina# rmmod loop
root@fedora:/home/rrobaina# time insmod /lib/modules/$(uname
-r)/kernel/drivers/block/loop.ko* max_loop=1000
real 0m23.419s
user 0m0.001s
sys 0m23.172s
Average:
real 0m22.991s
user 0m0.000s
sys 0m22.737s
Performance improvement: 51%
(46.405 - 22.737) / 46.405 = 0.510
Sorry for the extra trouble!
Best regards,
-Ricardo
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