Date: Fri, 05 Jun 2015 20:53:31 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Neel Natu <neelnatu@gmail.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: [CFR] Replacing while loops with proper division and multiplication Message-ID: <5571F02B.4080907@selasky.org> In-Reply-To: <CAFgRE9HOmzv%2BSuzWjsKDtsgRJCP3LpGJEQmd02_V=35__OE91A@mail.gmail.com> References: <55714B26.6060802@selasky.org> <CAFgRE9HOmzv%2BSuzWjsKDtsgRJCP3LpGJEQmd02_V=35__OE91A@mail.gmail.com>
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On 06/05/15 20:31, Neel Natu wrote:
>>> - runs = 0;
>>> >>- while (now >= state->nexthard) {
>>> >>- state->nexthard += tick_sbt;
>>> >>- runs++;
>>> >>- }
>>> >>- if (runs) {
>>> >>+ runs = (now - state->nexthard) / tick_sbt;
>>> >>+ if (runs > 0) {
>>> >>+ printf("R%d ", (int)runs);
>>> >>+ state->nexthard += tick_sbt * runs;
>>> >> hct = DPCPU_PTR(hardclocktime);
>>> >> *hct = state->nexthard - tick_sbt;
>>> >> if (fake < 2) {
> There is a difference in behavior in the two implementations when 'now
> == state->nexthard'. In the loop-based implementation this would end
> up with 'runs = 1' whereas in the division-based implementation it
> would end up with 'runs = 0'.
>
> I am not sure if this is intentional or just an oversight.
Hi Neel,
The nexthard is mainly updated in this piece of code. We can assume that
"state->nexthard" is aligned to "ticks_sbt". If "state->nexthard %
ticks_sbt == 0", is that still an issue?
--HPS
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