Hey Linus,
/* Summary */
The performance of /proc/kcore reads has been showing up as a bottleneck
for the drgn debugger. drgn scripts often spend ~25% of their time in the
kernel reading from /proc/kcore.
A lot of this overhead comes from silly inefficiencies. This pull
request contains fixes for the low-hanging fruit. The fixes are all
fairly small and straightforward. The result is a 25% improvement in
read latency in micro-benchmarks (from ~235 nanoseconds to ~175) and a
15% improvement in execution time for real-world drgn scripts:
- Make /proc/kcore entry permanent.
- Avoid walking the list on every read.
- Use percpu_rw_semaphore for kclist_lock.
- Make Omar Sandoval the official maintainer for /proc/kcore.
/* Testing */
gcc version 14.2.0 (Debian 14.2.0-6)
Debian clang version 16.0.6 (27+b1)
No build failures or warnings were observed.
/* Conflicts */
Merge conflicts with mainline
=============================
No known conflicts.
Merge conflicts with other trees
================================
No known conflicts.
The following changes since commit 40384c840ea1944d7c5a392e8975ed088ecf0b37:
Linux 6.13-rc1 (2024-12-01 14:28:56 -0800)
are available in the Git repository at:
git@xxxxxxxxxxxxxxxxxxx:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-6.14-rc1.kcore
for you to fetch changes up to 4972226d0dc48ddedf071355ca664fbf34b509c8:
Merge patch series "proc/kcore: performance optimizations" (2024-12-02 11:21:07 +0100)
Please consider pulling these changes from the signed vfs-6.14-rc1.kcore tag.
Thanks!
Christian
----------------------------------------------------------------
vfs-6.14-rc1.kcore
----------------------------------------------------------------
Christian Brauner (1):
Merge patch series "proc/kcore: performance optimizations"
Omar Sandoval (4):
proc/kcore: mark proc entry as permanent
proc/kcore: don't walk list on every read
proc/kcore: use percpu_rw_semaphore for kclist_lock
MAINTAINERS: add me as /proc/kcore maintainer
MAINTAINERS | 7 +++++
fs/proc/kcore.c | 81 +++++++++++++++++++++++++++++----------------------------
2 files changed, 48 insertions(+), 40 deletions(-)
