Re: [Openipmi-developer] [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers
On Mon, Oct 02, 2023 at 10:55:17AM +0200, Joel Granados via B4 Relay wrote: > Changes in v2: > - Left the dangling comma in the ctl_table arrays. > - Link to v1: > https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca...@samsung.com Thanks! Pushed onto sysctl-next for wider testing. Luis ___ Openipmi-developer mailing list Openipmi-developer@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openipmi-developer
Re: [Openipmi-developer] [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers
On Mon, Oct 02, 2023 at 12:27:18PM +, Christophe Leroy wrote:
>
>
> Le 02/10/2023 à 10:55, Joel Granados via B4 Relay a écrit :
> > From: Joel Granados
> >
<--- snip --->
> > - The "yesall" config saves 2432 bytes [4]
> > - The "tiny" config saves 64 bytes [5]
> > * memory usage:
> > In this case there were no bytes saved because I do not have any
> > of the drivers in the patch. To measure it comment the printk in
> > `new_dir` and uncomment the if conditional in `new_links` [3].
> >
> > ---
> > Changes in v2:
> > - Left the dangling comma in the ctl_table arrays.
> > - Link to v1:
> > https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca...@samsung.com
> >
> > Comments/feedback greatly appreciated
>
> Same problem on powerpc CI tests, all boot target failed, most of them
> with similar OOPS, see
> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20231002-jag-sysctl_remove_empty_elem_drivers-v2-15-02dd0d46f...@samsung.com/
I found the culprit!. Here you are rebasing on top of v6.5.0-rc6 "INFO:
Looking for kernel version: 6.5.0-rc6-gbf2ac4d7d596". The error makes
sense becuase in that version we have not introduced the stopping
criteria based on the ctl_table array size, so the loop continues
looking for an empty sentinel past valid memory (and does not find it).
The ctl_table check catches it but then fails to do a proper error
because we have already tried to access invalid memory. The solution
here is to make sure to rebase in on top of the latest rc in v6.6.
>
> What is strange is that I pushed your series into my github account, and
> got no failure, see https://github.com/chleroy/linux/actions/runs/6378951278
And here it works because you use the latest rc : "INFO: Looking for
kernel version: 6.6.0-rc3-g23d4b5db743c"
>
> Christophe
>
> >
> > Best
> >
> > Joel
> >
> > [1]
> > We are able to remove a sentinel table without behavioral change by
> > introducing a table_size argument in the same place where procname is
> > checked for NULL. The idea is for it to keep stopping when it hits
> > ->procname == NULL, while the sentinel is still present. And when the
> > sentinel is removed, it will stop on the table_size. You can go to
> > (https://lore.kernel.org/all/20230809105006.1198165-1-j.grana...@samsung.com/)
> > for more information.
> >
> > [2]
> > Links Related to the ctl_table sentinel removal:
> > * Good summary from Luis sent with the "pull request" for the
> >preparation patches.
> >https://lore.kernel.org/all/zo5yx5jfoggi%2f...@bombadil.infradead.org/
> > * Another very good summary from Luis.
> >https://lore.kernel.org/all/zmfizkfkvxuft...@bombadil.infradead.org/
> > * This is a patch set that replaces register_sysctl_table with
> > register_sysctl
> >https://lore.kernel.org/all/20230302204612.782387-1-mcg...@kernel.org/
> > * Patch set to deprecate register_sysctl_paths()
> >https://lore.kernel.org/all/20230302202826.776286-1-mcg...@kernel.org/
> > * Here there is an explicit expectation for the removal of the sentinel
> > element.
> >https://lore.kernel.org/all/20230321130908.6972-1-frank...@vivo.com
> > * The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
> >https://lore.kernel.org/all/20220220060626.15885-1-tangm...@uniontech.com
> >
> > [3]
> > To measure the in memory savings apply this on top of this patchset.
> >
> > "
> > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> > index c88854df0b62..e0073a627bac 100644
> > --- a/fs/proc/proc_sysctl.c
> > +++ b/fs/proc/proc_sysctl.c
> > @@ -976,6 +976,8 @@ static struct ctl_dir *new_dir(struct ctl_table_set
> > *set,
> > table[0].procname = new_name;
> > table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
> > init_header(>header, set->dir.header.root, set, node, table,
> > 1);
> > + // Counts additional sentinel used for each new dir.
> > + printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
> >
> > return new;
> > }
> > @@ -1199,6 +1201,9 @@ static struct ctl_table_header *new_links(struct
> > ctl_dir *dir, struct ctl_table_
> > link_name += len;
> > link++;
> > }
> > + // Counts additional sentinel used for each new registration
> > + //if ((head->ctl_table + head->ctl_table_size)->procname)
> > + printk("%ld sysctl saved mem kzalloc \n", sizeof(struct
> > ctl_table));
> > init_header(links, dir->header.root, dir->header.set, node,
> > link_table,
> > head->ctl_table_size);
> > links->nreg = nr_entries;
> > "
> > and then run the following bash script in the kernel:
> >
> > accum=0
> > for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do
> > echo $n
> > accum=$(calc "$accum + $n")
> > done
> > echo $accum
> >
> > [4]
> > add/remove: 0/0 grow/shrink: 0/21 up/down: 0/-2432 (-2432)
> >
Re: [Openipmi-developer] [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers
Le 02/10/2023 à 10:55, Joel Granados via B4 Relay a écrit : > From: Joel Granados > > What? > These commits remove the sentinel element (last empty element) from the > sysctl arrays of all the files under the "drivers/" directory that use a > sysctl array for registration. The merging of the preparation patches > (in https://lore.kernel.org/all/zo5yx5jfoggi%2f...@bombadil.infradead.org/) > to mainline allows us to just remove sentinel elements without changing > behavior (more info here [1]). > > These commits are part of a bigger set (here > https://github.com/Joelgranados/linux/tree/tag/sysctl_remove_empty_elem_V4) > that remove the ctl_table sentinel. Make the review process easier by > chunking the commits into manageable pieces. Each chunk can be reviewed > separately without noise from parallel sets. > > Now that the architecture chunk has been mostly reviewed [6], we send > the "drivers/" directory. Once this one is done, it will be follwed by > "fs/*", "kernel/*", "net/*" and miscellaneous. The final set will remove > the unneeded check for ->procname == NULL. > > Why? > By removing the sysctl sentinel elements we avoid kernel bloat as > ctl_table arrays get moved out of kernel/sysctl.c into their own > respective subsystems. This move was started long ago to avoid merge > conflicts; the sentinel removal bit came after Mathew Wilcox suggested > it to avoid bloating the kernel by one element as arrays moved out. This > patchset will reduce the overall build time size of the kernel and run > time memory bloat by about ~64 bytes per declared ctl_table array. I > have consolidated some links that shed light on the history of this > effort [2]. > > Testing: > * Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh) > * Ran this through 0-day with no errors or warnings > > Size saving after removing all sentinels: >These are the bytes that we save after removing all the sentinels >(this plus all the other chunks). I included them to get an idea of >how much memory we are talking about. > * bloat-o-meter: > - The "yesall" configuration results save 9158 bytes > > https://lore.kernel.org/all/20230621091000.424843-1-j.grana...@samsung.com/ > - The "tiny" config + CONFIG_SYSCTL save 1215 bytes > > https://lore.kernel.org/all/20230809105006.1198165-1-j.grana...@samsung.com/ > * memory usage: > In memory savings are measured to be 7296 bytes. (here is how to > measure [3]) > > Size saving after this patchset: > * bloat-o-meter > - The "yesall" config saves 2432 bytes [4] > - The "tiny" config saves 64 bytes [5] > * memory usage: > In this case there were no bytes saved because I do not have any > of the drivers in the patch. To measure it comment the printk in > `new_dir` and uncomment the if conditional in `new_links` [3]. > > --- > Changes in v2: > - Left the dangling comma in the ctl_table arrays. > - Link to v1: > https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca...@samsung.com > > Comments/feedback greatly appreciated Same problem on powerpc CI tests, all boot target failed, most of them with similar OOPS, see https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20231002-jag-sysctl_remove_empty_elem_drivers-v2-15-02dd0d46f...@samsung.com/ What is strange is that I pushed your series into my github account, and got no failure, see https://github.com/chleroy/linux/actions/runs/6378951278 Christophe > > Best > > Joel > > [1] > We are able to remove a sentinel table without behavioral change by > introducing a table_size argument in the same place where procname is > checked for NULL. The idea is for it to keep stopping when it hits > ->procname == NULL, while the sentinel is still present. And when the > sentinel is removed, it will stop on the table_size. You can go to > (https://lore.kernel.org/all/20230809105006.1198165-1-j.grana...@samsung.com/) > for more information. > > [2] > Links Related to the ctl_table sentinel removal: > * Good summary from Luis sent with the "pull request" for the >preparation patches. >https://lore.kernel.org/all/zo5yx5jfoggi%2f...@bombadil.infradead.org/ > * Another very good summary from Luis. >https://lore.kernel.org/all/zmfizkfkvxuft...@bombadil.infradead.org/ > * This is a patch set that replaces register_sysctl_table with register_sysctl >https://lore.kernel.org/all/20230302204612.782387-1-mcg...@kernel.org/ > * Patch set to deprecate register_sysctl_paths() >https://lore.kernel.org/all/20230302202826.776286-1-mcg...@kernel.org/ > * Here there is an explicit expectation for the removal of the sentinel > element. >https://lore.kernel.org/all/20230321130908.6972-1-frank...@vivo.com > * The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread >https://lore.kernel.org/all/20220220060626.15885-1-tangm...@uniontech.com > > [3] >
[Openipmi-developer] [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers
From: Joel Granados
What?
These commits remove the sentinel element (last empty element) from the
sysctl arrays of all the files under the "drivers/" directory that use a
sysctl array for registration. The merging of the preparation patches
(in https://lore.kernel.org/all/zo5yx5jfoggi%2f...@bombadil.infradead.org/)
to mainline allows us to just remove sentinel elements without changing
behavior (more info here [1]).
These commits are part of a bigger set (here
https://github.com/Joelgranados/linux/tree/tag/sysctl_remove_empty_elem_V4)
that remove the ctl_table sentinel. Make the review process easier by
chunking the commits into manageable pieces. Each chunk can be reviewed
separately without noise from parallel sets.
Now that the architecture chunk has been mostly reviewed [6], we send
the "drivers/" directory. Once this one is done, it will be follwed by
"fs/*", "kernel/*", "net/*" and miscellaneous. The final set will remove
the unneeded check for ->procname == NULL.
Why?
By removing the sysctl sentinel elements we avoid kernel bloat as
ctl_table arrays get moved out of kernel/sysctl.c into their own
respective subsystems. This move was started long ago to avoid merge
conflicts; the sentinel removal bit came after Mathew Wilcox suggested
it to avoid bloating the kernel by one element as arrays moved out. This
patchset will reduce the overall build time size of the kernel and run
time memory bloat by about ~64 bytes per declared ctl_table array. I
have consolidated some links that shed light on the history of this
effort [2].
Testing:
* Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh)
* Ran this through 0-day with no errors or warnings
Size saving after removing all sentinels:
These are the bytes that we save after removing all the sentinels
(this plus all the other chunks). I included them to get an idea of
how much memory we are talking about.
* bloat-o-meter:
- The "yesall" configuration results save 9158 bytes
https://lore.kernel.org/all/20230621091000.424843-1-j.grana...@samsung.com/
- The "tiny" config + CONFIG_SYSCTL save 1215 bytes
https://lore.kernel.org/all/20230809105006.1198165-1-j.grana...@samsung.com/
* memory usage:
In memory savings are measured to be 7296 bytes. (here is how to
measure [3])
Size saving after this patchset:
* bloat-o-meter
- The "yesall" config saves 2432 bytes [4]
- The "tiny" config saves 64 bytes [5]
* memory usage:
In this case there were no bytes saved because I do not have any
of the drivers in the patch. To measure it comment the printk in
`new_dir` and uncomment the if conditional in `new_links` [3].
---
Changes in v2:
- Left the dangling comma in the ctl_table arrays.
- Link to v1:
https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca...@samsung.com
Comments/feedback greatly appreciated
Best
Joel
[1]
We are able to remove a sentinel table without behavioral change by
introducing a table_size argument in the same place where procname is
checked for NULL. The idea is for it to keep stopping when it hits
->procname == NULL, while the sentinel is still present. And when the
sentinel is removed, it will stop on the table_size. You can go to
(https://lore.kernel.org/all/20230809105006.1198165-1-j.grana...@samsung.com/)
for more information.
[2]
Links Related to the ctl_table sentinel removal:
* Good summary from Luis sent with the "pull request" for the
preparation patches.
https://lore.kernel.org/all/zo5yx5jfoggi%2f...@bombadil.infradead.org/
* Another very good summary from Luis.
https://lore.kernel.org/all/zmfizkfkvxuft...@bombadil.infradead.org/
* This is a patch set that replaces register_sysctl_table with register_sysctl
https://lore.kernel.org/all/20230302204612.782387-1-mcg...@kernel.org/
* Patch set to deprecate register_sysctl_paths()
https://lore.kernel.org/all/20230302202826.776286-1-mcg...@kernel.org/
* Here there is an explicit expectation for the removal of the sentinel element.
https://lore.kernel.org/all/20230321130908.6972-1-frank...@vivo.com
* The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
https://lore.kernel.org/all/20220220060626.15885-1-tangm...@uniontech.com
[3]
To measure the in memory savings apply this on top of this patchset.
"
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index c88854df0b62..e0073a627bac 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -976,6 +976,8 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
table[0].procname = new_name;
table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
init_header(>header, set->dir.header.root, set, node, table, 1);
+ // Counts additional sentinel used for each new dir.
+ printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
return new;
}
@@ -1199,6 +1201,9 @@ static struct ctl_table_header
