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Re: [PATCH] s390: optimize syscall function
On 06/19/2017 09:03 AM, Christian Borntraeger wrote:
On 06/12/2017 03:57 PM, Martin Schwidefsky wrote:
On Mon, 12 Jun 2017 08:06:36 -0400
Zack Weinberg <firstname.lastname@example.org> wrote:
On Mon, Jun 12, 2017 at 1:49 AM, Martin Schwidefsky
On Fri, 9 Jun 2017 13:29:07 +0200
Christian Borntraeger <email@example.com> wrote:
Since kernel 2.6.0 all Linux version accept the system call number
in register 1 for svc 0. There is no need to have special handling
that uses EX for system calls < 256. This will simplify and speed
up that code.
A microbenchmark doing "syscall(__NR_getpid);" in a loops gets faster
* sysdeps/unix/sysv/linux/s390/s390-64/syscall.S: Simplify
code by always using SVC 0 instead of EX.
* sysdeps/unix/sysv/linux/s390/s390-64/syscall.S: Likewise.
Signed-off-by: Christian Borntraeger <firstname.lastname@example.org>
sysdeps/unix/sysv/linux/s390/s390-32/syscall.S | 12 +++---------
sysdeps/unix/sysv/linux/s390/s390-64/syscall.S | 12 +++---------
2 files changed, 6 insertions(+), 18 deletions(-)
NAK. E.g. this from glibc:
Uh, I believe Christian was proposing to change the exact code you are
quoting. Did you think he was proposing to remove backward
compatibility for EX from the kernel-side syscall path?
Exactly, this is a glibc patch :-)
The mimimum kernel version for glibc is high enough, so that the kernel
will always understand svc 0, which allows us to get rid of ex in glibc
Indeed, I was thinking too much about the kernel side of things.
This patch is okay.