On 11/16/2010 11:08 PM, Jeremy Fitzhardinge wrote: > From: Jeremy Fitzhardinge<jeremy.fitzhardinge@xxxxxxxxxx> > > Hi all, > > This is a revised version of the pvticket lock series. > > The early part of the series is mostly unchanged: it converts the bulk > of the ticket lock code into C and makes the "small" and "large" > ticket code common. The only changes are the incorporation of various > review comments. > > The latter part of the series converts from pv spinlocks to pv ticket > locks (ie, using the ticket lock fastpath as-is, but adding pv ops for > the ticketlock slowpaths). > > The significant difference here is that rather than adding a new > ticket_t-sized element to arch_spinlock_t - effectively doubling the > size - I steal the LSB of the tickets themselves to store a bit. This > allows the structure to remain the same size, but at the cost of > halving the max number of CPUs (127 for a 8-bit ticket, and a hard max > of 32767 overall). > > The extra bit (well, two, but one is unused) in indicates whether the > lock has gone into "slowpath state", which means one of its lockers > has entered its slowpath and has blocked in the hypervisor. This > means the current lock-holder needs to make sure it gets kicked out of > the hypervisor on unlock. > > The spinlock remains in slowpath state until the last unlock happens > (ie there are no more queued lockers). > > This code survives for a while with moderate testing, (make -j 100 on > 8 VCPUs on a 4 PCPU system), but locks up after about 20 iterations, > so there's still some race/deadlock in there (probably something > misordered), but I think the basic approach is sound. This is going to be very useful for kvm; I'd like to see the fixed version gets merged. -- error compiling committee.c: too many arguments to function _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
