| Message ID | 20220221095617.1974-1-longpeng2@huawei.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | qemu-sem-posix: use monotonic clock instead | expand |
On 2/21/22 10:56, Longpeng(Mike) via wrote: > The qemu_sem_timedwait() uses system time as default, it would be affected by > changes to the system time. In the real scenario, the time that goes faster or > slower is a common case and the NTP service could help us to sync time > periodically. > > This patchset uses monotonic clock instead of the realtime clock, this could > make sure we would not be affected by the system time anymore. This looks good, I don't think there are cases where a more optimized semaphore is necessary (if there were, we could introduce a futex fallback on Linux). However, pthread_condattr_t need not be in the struct. The attributes can be allocated on the stack, because they do not have to remain alive after pthread_cond_init. Thanks, Paolo > Longpeng (Mike) (2): > sem-posix: remove the posix semaphore support > sem-posix: use monotonic clock instead > > include/qemu/thread-posix.h | 5 +-- > meson.build | 12 ++++++- > util/qemu-thread-posix.c | 82 +++++++++++++++------------------------------ > 3 files changed, 39 insertions(+), 60 deletions(-) >
> -----Original Message----- > From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo Bonzini > Sent: Monday, February 21, 2022 7:31 PM > To: Longpeng (Mike, Cloud Infrastructure Service Product Dept.) > <longpeng2@huawei.com>; berrange@redhat.com; mst@redhat.com > Cc: qemu-devel@nongnu.org; Gonglei (Arei) <arei.gonglei@huawei.com> > Subject: Re: [RFC 0/2] qemu-sem-posix: use monotonic clock instead > > On 2/21/22 10:56, Longpeng(Mike) via wrote: > > The qemu_sem_timedwait() uses system time as default, it would be affected > by > > changes to the system time. In the real scenario, the time that goes faster > or > > slower is a common case and the NTP service could help us to sync time > > periodically. > > > > This patchset uses monotonic clock instead of the realtime clock, this could > > make sure we would not be affected by the system time anymore. > > This looks good, I don't think there are cases where a more optimized > semaphore is necessary (if there were, we could introduce a futex > fallback on Linux). > > However, pthread_condattr_t need not be in the struct. The attributes > can be allocated on the stack, because they do not have to remain alive > after pthread_cond_init. > OK, will do in the next version, thanks! > Thanks, > > Paolo > > > Longpeng (Mike) (2): > > sem-posix: remove the posix semaphore support > > sem-posix: use monotonic clock instead > > > > include/qemu/thread-posix.h | 5 +-- > > meson.build | 12 ++++++- > > util/qemu-thread-posix.c | 82 > +++++++++++++++------------------------------ > > 3 files changed, 39 insertions(+), 60 deletions(-) > >