| Message ID | cover.1709127473.git.geert+renesas@glider.be (mailing list archive) |
|---|---|
| Headers | show |
| Series | printk_index: Fix false positives | expand |
On Wed, Feb 28, 2024 at 03:00:01PM +0100, Geert Uytterhoeven wrote: > Hi all, > > When printk-indexing is enabled, each printk() invocation emits a > pi_entry structure, containing the format string and other information > related to its location in the kernel sources. This is even true when > the printk() is protected by an always-false check, as is typically the > case for debug messages: while the actual code to print the message is > optimized out by the compiler, the pi_entry structure is still emitted. > Hence when debugging is disabled, this leads to the inclusion in the > index of lots of printk formats that cannot be emitted by the current > kernel. > > This series fixes that for the common debug helpers under include/. > It reduces the size of an arm64 defconfig kernel with > CONFIG_PRINTK_INDEX=y by ca. 1.5 MiB, or 28% of the overhead of > enabling CONFIG_PRINTK_INDEX=y. > > Notes: > - netdev_(v)dbg() and netif_(v)dbg() are not affected, as > net{dev,if}_printk() do not implement printk-indexing, except > for the single global internal instance of __netdev_printk(). > - This series fixes only debug code in global header files under > include/. There are more cases to fix in subsystem-specific header > files and in sources files. The whole series makes a lot of sense and gives a good examples for above mentioned subsystem specific code on how to do it in a better way. Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
On 2/28/24 22:00, Geert Uytterhoeven wrote: > Hi all, > > When printk-indexing is enabled, each printk() invocation emits a > pi_entry structure, containing the format string and other information > related to its location in the kernel sources. This is even true when > the printk() is protected by an always-false check, as is typically the > case for debug messages: while the actual code to print the message is > optimized out by the compiler, the pi_entry structure is still emitted. > Hence when debugging is disabled, this leads to the inclusion in the > index of lots of printk formats that cannot be emitted by the current > kernel. > > This series fixes that for the common debug helpers under include/. > It reduces the size of an arm64 defconfig kernel with > CONFIG_PRINTK_INDEX=y by ca. 1.5 MiB, or 28% of the overhead of > enabling CONFIG_PRINTK_INDEX=y. > > Notes: > - netdev_(v)dbg() and netif_(v)dbg() are not affected, as > net{dev,if}_printk() do not implement printk-indexing, except > for the single global internal instance of __netdev_printk(). > - This series fixes only debug code in global header files under > include/. There are more cases to fix in subsystem-specific header > files and in sources files. > > Thanks for your comments! > > Geert Uytterhoeven (4): > printk: Let no_printk() use _printk() > dev_printk: Add and use dev_no_printk() > dyndbg: Use *no_printk() helpers > ceph: Use no_printk() helper > > include/linux/ceph/ceph_debug.h | 18 +++++++----------- > include/linux/dev_printk.h | 25 +++++++++++++------------ > include/linux/dynamic_debug.h | 4 ++-- > include/linux/printk.h | 2 +- > 4 files changed, 23 insertions(+), 26 deletions(-) > This series LGTM. Reviewed-by: Xiubo Li <xiubli@redhat.com>
Thanks for working on this! This whole patchset looks good to me.
Reviewed-by: Chris Down <chris@chrisdown.name>
On Wed 2024-02-28 15:00:01, Geert Uytterhoeven wrote: > Hi all, > > When printk-indexing is enabled, each printk() invocation emits a > pi_entry structure, containing the format string and other information > related to its location in the kernel sources. This is even true when > the printk() is protected by an always-false check, as is typically the > case for debug messages: while the actual code to print the message is > optimized out by the compiler, the pi_entry structure is still emitted. > Hence when debugging is disabled, this leads to the inclusion in the > index of lots of printk formats that cannot be emitted by the current > kernel. > > This series fixes that for the common debug helpers under include/. > It reduces the size of an arm64 defconfig kernel with > CONFIG_PRINTK_INDEX=y by ca. 1.5 MiB, or 28% of the overhead of > enabling CONFIG_PRINTK_INDEX=y. > > Notes: > - netdev_(v)dbg() and netif_(v)dbg() are not affected, as > net{dev,if}_printk() do not implement printk-indexing, except > for the single global internal instance of __netdev_printk(). > - This series fixes only debug code in global header files under > include/. There are more cases to fix in subsystem-specific header > files and in sources files. > > Thanks for your comments! > > Geert Uytterhoeven (4): > printk: Let no_printk() use _printk() > dev_printk: Add and use dev_no_printk() > dyndbg: Use *no_printk() helpers > ceph: Use no_printk() helper > > include/linux/ceph/ceph_debug.h | 18 +++++++----------- > include/linux/dev_printk.h | 25 +++++++++++++------------ > include/linux/dynamic_debug.h | 4 ++-- > include/linux/printk.h | 2 +- > 4 files changed, 23 insertions(+), 26 deletions(-) The whole series looks good to me: Reviewed-by: Petr Mladek <pmladek@suse.com> I am going take it via printk tree for 6.10. I am sorry that I haven't looked at it in time before the merge window for 6.9. I have been snowed under various tasks. The changes are not complicated. But they also are not critical to be pushed an expedite way. Best Regards, Petr
On Tue 2024-03-19 16:09:01, Petr Mladek wrote: > On Wed 2024-02-28 15:00:01, Geert Uytterhoeven wrote: > > Hi all, > > > > When printk-indexing is enabled, each printk() invocation emits a > > pi_entry structure, containing the format string and other information > > related to its location in the kernel sources. This is even true when > > the printk() is protected by an always-false check, as is typically the > > case for debug messages: while the actual code to print the message is > > optimized out by the compiler, the pi_entry structure is still emitted. > > Hence when debugging is disabled, this leads to the inclusion in the > > index of lots of printk formats that cannot be emitted by the current > > kernel. > > > > This series fixes that for the common debug helpers under include/. > > It reduces the size of an arm64 defconfig kernel with > > CONFIG_PRINTK_INDEX=y by ca. 1.5 MiB, or 28% of the overhead of > > enabling CONFIG_PRINTK_INDEX=y. > > > > Notes: > > - netdev_(v)dbg() and netif_(v)dbg() are not affected, as > > net{dev,if}_printk() do not implement printk-indexing, except > > for the single global internal instance of __netdev_printk(). > > - This series fixes only debug code in global header files under > > include/. There are more cases to fix in subsystem-specific header > > files and in sources files. > > > > Thanks for your comments! > > > > Geert Uytterhoeven (4): > > printk: Let no_printk() use _printk() > > dev_printk: Add and use dev_no_printk() > > dyndbg: Use *no_printk() helpers > > ceph: Use no_printk() helper > > > > include/linux/ceph/ceph_debug.h | 18 +++++++----------- > > include/linux/dev_printk.h | 25 +++++++++++++------------ > > include/linux/dynamic_debug.h | 4 ++-- > > include/linux/printk.h | 2 +- > > 4 files changed, 23 insertions(+), 26 deletions(-) > > The whole series looks good to me: > > Reviewed-by: Petr Mladek <pmladek@suse.com> > > I am going take it via printk tree for 6.10. JFYI, the patchset has been committed into printk/linux.git, branch for-6.10. Best Regards, Petr
Hi all, When printk-indexing is enabled, each printk() invocation emits a pi_entry structure, containing the format string and other information related to its location in the kernel sources. This is even true when the printk() is protected by an always-false check, as is typically the case for debug messages: while the actual code to print the message is optimized out by the compiler, the pi_entry structure is still emitted. Hence when debugging is disabled, this leads to the inclusion in the index of lots of printk formats that cannot be emitted by the current kernel. This series fixes that for the common debug helpers under include/. It reduces the size of an arm64 defconfig kernel with CONFIG_PRINTK_INDEX=y by ca. 1.5 MiB, or 28% of the overhead of enabling CONFIG_PRINTK_INDEX=y. Notes: - netdev_(v)dbg() and netif_(v)dbg() are not affected, as net{dev,if}_printk() do not implement printk-indexing, except for the single global internal instance of __netdev_printk(). - This series fixes only debug code in global header files under include/. There are more cases to fix in subsystem-specific header files and in sources files. Thanks for your comments! Geert Uytterhoeven (4): printk: Let no_printk() use _printk() dev_printk: Add and use dev_no_printk() dyndbg: Use *no_printk() helpers ceph: Use no_printk() helper include/linux/ceph/ceph_debug.h | 18 +++++++----------- include/linux/dev_printk.h | 25 +++++++++++++------------ include/linux/dynamic_debug.h | 4 ++-- include/linux/printk.h | 2 +- 4 files changed, 23 insertions(+), 26 deletions(-)