On 11/24/2017 12:29 AM, Thomas Gleixner wrote:
On Thu, 23 Nov 2017, Sagar Arun Kamble wrote:
We needed inputs on possible optimization that can be done to
timecounter/cyclecounter structures/usage.
This mail is in response to review of patch
https://patchwork.freedesktop.org/patch/188448/.
As Chris's observation below, about dozen of timecounter users in the kernel
have below structures
defined individually:
spinlock_t lock;
struct cyclecounter cc;
struct timecounter tc;
Can we move lock and cc to tc? That way it will be convenient.
Also it will allow unifying the locking/overflow watchdog handling across all
drivers.
Looks like none of the timecounter usage sites has a real need to separate
timecounter and cyclecounter.
Yes. Will share patch for this change.
The lock is a different question. The locking of the various drivers
differs and I have no idea how you want to handle that. Just sticking the
lock into the datastructure and then not making use of it in the
timercounter code and leave it to the callsites does not make sense.
Most of the locks are held around timecounter_read. In some instances it is
held when cyclecounter is
updated standalone or is updated along with timecounter calls.
Was thinking if we move the lock in timecounter functions, drivers just have to
do locking around its
operations on cyclecounter. But then another problem I see is there are
variation of locking calls
like lock_irqsave, lock_bh, write_lock_irqsave (some using rwlock_t). Should
this all locking be left
to driver only then?
Thanks,
tglx
Thanks
Sagar
