On Thu, 2022-09-08 at 01:25 +0800, Jiebin Sun wrote: > The msg_bytes and msg_hdrs atomic counters are frequently > updated when IPC msg queue is in heavy use, causing heavy > cache bounce and overhead. Change them to percpu_counter > greatly improve the performance. Since there is one percpu > struct per namespace, additional memory cost is minimal. > Reading of the count done in msgctl call, which is infrequent. > So the need to sum up the counts in each CPU is infrequent. > > > Apply the patch and test the pts/stress-ng-1.4.0 > -- system v message passing (160 threads). > > Score gain: 3.17x > > ... > > +/* large batch size could reduce the times to sum up percpu counter */ > +#define MSG_PERCPU_COUNTER_BATCH 1024 > + Jiebin, 1024 is a small size (1/4 page). The local per cpu counter could overflow to the gloabal count quickly if it is limited to this size, since our count tracks msg size. I'll suggest something larger, say 8*1024*1024, about 8MB to accommodate about 2 large page worth of data. Maybe that will further improve throughput on stress-ng by reducing contention on adding to the global count. Tim
