Re: [PATCH v4] powerpc/vdso64: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE

On 2017/10/10 09:03AM, Santosh Sivaraj wrote:

* Naveen N. Rao [off-list ref] wrote (on 2017-10-09 10:39:18 +0000):

quoted

On 2017/10/09 08:09AM, Santosh Sivaraj wrote:

[snip]

quoted

quoted

+	add     r3,r3,r0
+	ld      r0,CFG_TB_UPDATE_COUNT(r3)
+	cmpld   cr0,r0,r8               /* check if updated */
+	bne-    70b

I also notice that the code for dealing with CLOCK_MONOTONIC is similar 
for _COARSE and regular clocks. If possible, we should reuse that as 
well.

In this case we will be adding more checks and branches in order to reuse
the code. If we want to keep the code common we will have to do a lot of
jumping around, code will contain a bunch of branches, which I feel will make
the code/flow hard to understand. (Q: Does lot of branches have bad effect on
branch prediction?)

Right - like we discussed offline, if it hurts readability, that's a 
good enough reason not to do this. We are only talking about a few 
instructions here anyway, so no need to worry too much.

- Naveen