Messages in this thread | | | From | Sven Schnelle <> | Subject | [PATCH v2 0/3] entry: inline syscall enter/exit functions | Date | Mon, 18 Dec 2023 08:45:17 +0100 |
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Hi List,
looking into the performance of syscall entry/exit after s390 switched to generic entry showed that there's quite some overhead calling some of the entry/exit work functions even when there's nothing to do. This patchset moves the entry and exit function to entry-common.h, so non inlined code gets only called when there is some work pending.
I wrote a small program that just issues invalid syscalls in a loop. On an s390 machine, this results in the following numbers:
without this series:
$ ./syscall 1000000000 runtime: 94.886581s / per-syscall 9.488658e-08s
with this series:
$ ./syscall 1000000000 runtime: 84.732391s / per-syscall 8.473239e-08s
so the time required for one syscall dropped from 94.8ns to 84.7ns, which is a drop of about 11%.
Sven Schnelle (3): entry: move exit to usermode functions to header file entry: move enter_from_user_mode() to header file entry: move syscall_enter_from_user_mode() to header file
include/linux/entry-common.h | 94 +++++++++++++++++++++++++++++-- kernel/entry/common.c | 106 ++++------------------------------- 2 files changed, 100 insertions(+), 100 deletions(-)
Changes in v2: - don't move of exit_to_user_mode_loop() to header file -- 2.40.1
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