* Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > On Thu, 21 Jun 2018, Ingo Molnar wrote: > > > > > * Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > > > > > From: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > > Subject: [PATCH v2] x86: optimize memcpy_flushcache > > > > > > In the context of constant short length stores to persistent memory, > > > memcpy_flushcache suffers from a 2% performance degradation compared to > > > explicitly using the "movnti" instruction. > > > > > > Optimize 4, 8, and 16 byte memcpy_flushcache calls to explicitly use the > > > movnti instruction with inline assembler. > > > > Linus requested asm optimizations to include actual benchmarks, so it would be > > nice to describe how this was tested, on what hardware, and what the before/after > > numbers are. > > > > Thanks, > > > > Ingo > > It was tested on 4-core skylake machine with persistent memory being > emulated using the memmap kernel option. The dm-writecache target used the > emulated persistent memory as a cache and sata SSD as a backing device. > The patch results in 2% improved throughput when writing data using dd. > > I don't have access to the machine anymore. I think this information is enough, but do we know how well memmap emulation represents true persistent memory speed and cache management characteristics? It might be representative - but I don't know for sure, nor probably most readers of the changelog. So could you please put all this into an updated changelog, and also add a short description that outlines exactly which codepaths end up using this method in a typical persistent memory setup? All filesystem ops - or only reads, etc? Thanks, Ingo -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
