search for: flush_and_commit_buff

...her CLFLUSH instruction. For example, software can use an MFENCE instruction to ensure that previous stores are included in the write-back. There are instances of this in mwait_play_dead, clflush_cache_range, mwait_idle_with_hints, mwait_idle .. A comment near pcommit_sfence includes an example flush_and_commit_buffer code which is interesting - it assumes sfence flushes clflush. So it appears that pcommit_sfence in that file is wrong then? At least on processors where it falls back on clflush. mwait_idle is the only one that calls smp_mb and not mb() I couldn't figure out why - original patches did mb()...

...her CLFLUSH instruction. For example, software can use an MFENCE instruction to ensure that previous stores are included in the write-back. There are instances of this in mwait_play_dead, clflush_cache_range, mwait_idle_with_hints, mwait_idle .. A comment near pcommit_sfence includes an example flush_and_commit_buffer code which is interesting - it assumes sfence flushes clflush. So it appears that pcommit_sfence in that file is wrong then? At least on processors where it falls back on clflush. mwait_idle is the only one that calls smp_mb and not mb() I couldn't figure out why - original patches did mb()...

On Tue, Jan 12, 2016 at 02:25:24PM -0800, H. Peter Anvin wrote: > On 01/12/16 14:10, Michael S. Tsirkin wrote: > > mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's > > 2 to 3 times slower than lock; addl $0,(%%e/rsp) that we use on older CPUs. > > > > So let's use the locked variant everywhere - helps keep the code simple as >

On Tue, Jan 12, 2016 at 02:25:24PM -0800, H. Peter Anvin wrote: > On 01/12/16 14:10, Michael S. Tsirkin wrote: > > mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's > > 2 to 3 times slower than lock; addl $0,(%%e/rsp) that we use on older CPUs. > > > > So let's use the locked variant everywhere - helps keep the code simple as >