>> I suppose that calling gettimeofday() repeatedly (to add a timestamp to
>> some data) within the kernel is cheaper than doing it in userspace, is it?
>
> Well, the following daemon works on most archs that support mmap at only
[...]
Ah, it does not need to be that complex.
Just comparing two approaches:
--1--
/* KERNEL: Calling read() on a character device */
static int u_read(...) {
...
gettimeofday(tv);
enqueue_in_buffer(tv);
...
}
+nothing needed in userspace
--2--
/* KERNEL: No gettimeofday */
Userspace:
while(read(fd, buf, sizeof(buf)) {
gettimeofday(&buf.tv);
...
}
(In either case, at some point, userspace has a timestamp.)
I think that -1- is faster it does not require an additional syscall from
userspace to sys_gettimeofday().
Jan Engelhardt
--
No TOFU for me, please.
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