| Message ID | 1573041302-4904-4-git-send-email-zhenzhong.duan@oracle.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | misc fixes on halt-poll code for both KVM and guest | expand |
On Wednesday, November 6, 2019 12:55:01 PM CET Zhenzhong Duan wrote: > As user can adjust guest_halt_poll_grow_start and guest_halt_poll_ns > which leads to cpu_halt_poll_us beyond the two boundaries. This patch > ensures cpu_halt_poll_us in that scope. > > If guest_halt_poll_shrink is 0, shrink the cpu_halt_poll_us to > guest_halt_poll_grow_start instead of 0. To disable poll we can set > guest_halt_poll_ns to 0. > > If user wrongly set guest_halt_poll_grow_start > guest_halt_poll_ns > 0, > guest_halt_poll_ns take precedency and poll time is a fixed value of > guest_halt_poll_ns. > > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> > --- > drivers/cpuidle/governors/haltpoll.c | 28 +++++++++++++--------------- > 1 file changed, 13 insertions(+), 15 deletions(-) > > diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c > index 660859d..4a39df4 100644 > --- a/drivers/cpuidle/governors/haltpoll.c > +++ b/drivers/cpuidle/governors/haltpoll.c > @@ -97,32 +97,30 @@ static int haltpoll_select(struct cpuidle_driver *drv, > > static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us) > { > - unsigned int val; > + unsigned int val = dev->poll_limit_ns; Not necessary to initialize it here. > u64 block_ns = block_us*NSEC_PER_USEC; > > /* Grow cpu_halt_poll_us if > - * cpu_halt_poll_us < block_ns < guest_halt_poll_us > + * cpu_halt_poll_us < block_ns <= guest_halt_poll_us You could update the comment to say "dev->poll_limit_ns" instead of "cpu_halt_poll_us" while at it. > */ > - if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) { > + if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns && > + guest_halt_poll_grow) The "{" brace is still needed as per the coding style and I'm not sure why to avoid guest_halt_poll_grow equal to zero here? > val = dev->poll_limit_ns * guest_halt_poll_grow; > - > - if (val < guest_halt_poll_grow_start) > - val = guest_halt_poll_grow_start; > - if (val > guest_halt_poll_ns) > - val = guest_halt_poll_ns; > - > - dev->poll_limit_ns = val; > - } else if (block_ns > guest_halt_poll_ns && > - guest_halt_poll_allow_shrink) { > + else if (block_ns > guest_halt_poll_ns && > + guest_halt_poll_allow_shrink) { > unsigned int shrink = guest_halt_poll_shrink; > > - val = dev->poll_limit_ns; > if (shrink == 0) > - val = 0; > + val = guest_halt_poll_grow_start; That's going to be corrected below, so the original code would be fine. > else > val /= shrink; Here you can do val = dev->poll_limit_ns / shrink; > - dev->poll_limit_ns = val; > } > + if (val < guest_halt_poll_grow_start) > + val = guest_halt_poll_grow_start; Note that guest_halt_poll_grow_start is in us (as per the comment next to its definition and the initial value). That is a bug in the original code too, but anyway. > + if (val > guest_halt_poll_ns) > + val = guest_halt_poll_ns; > + > + dev->poll_limit_ns = val; > } > > /** >
On 2019/11/15 18:45, Rafael J. Wysocki wrote: > On Wednesday, November 6, 2019 12:55:01 PM CET Zhenzhong Duan wrote: >> As user can adjust guest_halt_poll_grow_start and guest_halt_poll_ns >> which leads to cpu_halt_poll_us beyond the two boundaries. This patch >> ensures cpu_halt_poll_us in that scope. >> >> If guest_halt_poll_shrink is 0, shrink the cpu_halt_poll_us to >> guest_halt_poll_grow_start instead of 0. To disable poll we can set >> guest_halt_poll_ns to 0. >> >> If user wrongly set guest_halt_poll_grow_start > guest_halt_poll_ns > 0, >> guest_halt_poll_ns take precedency and poll time is a fixed value of >> guest_halt_poll_ns. >> >> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> >> --- >> drivers/cpuidle/governors/haltpoll.c | 28 +++++++++++++--------------- >> 1 file changed, 13 insertions(+), 15 deletions(-) >> >> diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c >> index 660859d..4a39df4 100644 >> --- a/drivers/cpuidle/governors/haltpoll.c >> +++ b/drivers/cpuidle/governors/haltpoll.c >> @@ -97,32 +97,30 @@ static int haltpoll_select(struct cpuidle_driver *drv, >> >> static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us) >> { >> - unsigned int val; >> + unsigned int val = dev->poll_limit_ns; > Not necessary to initialize it here. Then an random val may bypass all the check and get assigned to dev->poll_limit_ns if guest_halt_poll_grow_start< block_ns< uninitialized val< guest_halt_poll_ns With my change, dev->poll_limit_ns will not be changed in that case, logic same as original code. > >> u64 block_ns = block_us*NSEC_PER_USEC; >> >> /* Grow cpu_halt_poll_us if >> - * cpu_halt_poll_us < block_ns < guest_halt_poll_us >> + * cpu_halt_poll_us < block_ns <= guest_halt_poll_us > You could update the comment to say "dev->poll_limit_ns" instead of > "cpu_halt_poll_us" while at it. Will do, also guest_halt_poll_us to guest_halt_poll_ns > >> */ >> - if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) { >> + if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns && >> + guest_halt_poll_grow) > The "{" brace is still needed as per the coding style and I'm not sure why > to avoid guest_halt_poll_grow equal to zero here? Will add "{}" and remove guest_halt_poll_grow check. My inital thought was to prevent dev->poll_limit_ns get shrinked with guest_halt_poll_grow=0. > >> val = dev->poll_limit_ns * guest_halt_poll_grow; >> - >> - if (val < guest_halt_poll_grow_start) >> - val = guest_halt_poll_grow_start; >> - if (val > guest_halt_poll_ns) >> - val = guest_halt_poll_ns; >> - >> - dev->poll_limit_ns = val; >> - } else if (block_ns > guest_halt_poll_ns && >> - guest_halt_poll_allow_shrink) { >> + else if (block_ns > guest_halt_poll_ns && >> + guest_halt_poll_allow_shrink) { >> unsigned int shrink = guest_halt_poll_shrink; >> >> - val = dev->poll_limit_ns; >> if (shrink == 0) >> - val = 0; >> + val = guest_halt_poll_grow_start; > That's going to be corrected below, so the original code would be fine. val was assigned twice using 'val = 0' while it's once with my change, optimal a bit? > >> else >> val /= shrink; > Here you can do > > val = dev->poll_limit_ns / shrink; Any special reason？Looks no difference for me. > >> - dev->poll_limit_ns = val; >> } >> + if (val < guest_halt_poll_grow_start) >> + val = guest_halt_poll_grow_start; > Note that guest_halt_poll_grow_start is in us (as per the comment next to its > definition and the initial value). That is a bug in the original code too, > but anyway. Good catch! will fix the comment. The default 50000ns vs 50000us, looks author means ns. guest_halt_poll_ns defaults to 200000, also hints ns for guest_halt_poll_grow_start. Thanks Zhenzhong
diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c index 660859d..4a39df4 100644 --- a/drivers/cpuidle/governors/haltpoll.c +++ b/drivers/cpuidle/governors/haltpoll.c @@ -97,32 +97,30 @@ static int haltpoll_select(struct cpuidle_driver *drv, static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us) { - unsigned int val; + unsigned int val = dev->poll_limit_ns; u64 block_ns = block_us*NSEC_PER_USEC; /* Grow cpu_halt_poll_us if - * cpu_halt_poll_us < block_ns < guest_halt_poll_us + * cpu_halt_poll_us < block_ns <= guest_halt_poll_us */ - if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) { + if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns && + guest_halt_poll_grow) val = dev->poll_limit_ns * guest_halt_poll_grow; - - if (val < guest_halt_poll_grow_start) - val = guest_halt_poll_grow_start; - if (val > guest_halt_poll_ns) - val = guest_halt_poll_ns; - - dev->poll_limit_ns = val; - } else if (block_ns > guest_halt_poll_ns && - guest_halt_poll_allow_shrink) { + else if (block_ns > guest_halt_poll_ns && + guest_halt_poll_allow_shrink) { unsigned int shrink = guest_halt_poll_shrink; - val = dev->poll_limit_ns; if (shrink == 0) - val = 0; + val = guest_halt_poll_grow_start; else val /= shrink; - dev->poll_limit_ns = val; } + if (val < guest_halt_poll_grow_start) + val = guest_halt_poll_grow_start; + if (val > guest_halt_poll_ns) + val = guest_halt_poll_ns; + + dev->poll_limit_ns = val; } /**
As user can adjust guest_halt_poll_grow_start and guest_halt_poll_ns which leads to cpu_halt_poll_us beyond the two boundaries. This patch ensures cpu_halt_poll_us in that scope. If guest_halt_poll_shrink is 0, shrink the cpu_halt_poll_us to guest_halt_poll_grow_start instead of 0. To disable poll we can set guest_halt_poll_ns to 0. If user wrongly set guest_halt_poll_grow_start > guest_halt_poll_ns > 0, guest_halt_poll_ns take precedency and poll time is a fixed value of guest_halt_poll_ns. Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> --- drivers/cpuidle/governors/haltpoll.c | 28 +++++++++++++--------------- 1 file changed, 13 insertions(+), 15 deletions(-)