On 10/11/2017 02:48 PM, Peter Zijlstra wrote: > On Wed, Oct 11, 2017 at 02:01:51PM -0400, Waiman Long wrote: >> # of Patches Reader Writer >> Applied Locking Rate Locking Rate >> ------------ ------------ ------------ >> 0 5,155/ 5,155/ 5,155 5,154/248,852/346,281 >> 7 5,696/ 5,697/ 5,698 113,500/215,826/320,872 >> 8 4,827/ 5,047/ 5,215 4,826/176,797/284,069 >> 9 211,276/ 509,712/1,134,007 4,894/221,839/246,818 >> 11 884,513/1,043,989/1,252,533 9,604/ 11,105/ 25,225 >> >> It can be seen that rwsem changes from writer-preferring to >> reader-preferring. > A bit radically so, you almost starve the writers there. Yes, almost, but the lock handoff code will make sure that it won't actually get starved. That is why I added aggressive reader lock stealing after the lock handoff code. Cheers, Longman
