search for: clflush_cache_range

...instruction. It is not guaranteed to be ordered by any other fencing or serializing instructions or by another 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. mwai...

...instruction. It is not guaranteed to be ordered by any other fencing or serializing instructions or by another 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. mwai...

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 >