On 2/24/25 02:36, Suren Baghdasaryan wrote: > On Sat, Feb 22, 2025 at 8:44 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: >> >> Don't know about this particular part but testing sheaves with maple >> node cache and stress testing mmap/munmap syscalls shows performance >> benefits as long as there is some delay to let kfree_rcu() do its job. >> I'm still gathering results and will most likely post them tomorrow. Without such delay, the perf is same or worse? > Here are the promised test results: > > First I ran an Android app cycle test comparing the baseline against sheaves > used for maple tree nodes (as this patchset implements). I registered about > 3% improvement in app launch times, indicating improvement in mmap syscall > performance. There was no artificial 500us delay added for this test, right? > Next I ran an mmap stress test which maps 5 1-page readable file-backed > areas, faults them in and finally unmaps them, timing mmap syscalls. > Repeats that 200000 cycles and reports the total time. Average of 10 such > runs is used as the final result. > 3 configurations were tested: > > 1. Sheaves used for maple tree nodes only (this patchset). > > 2. Sheaves used for maple tree nodes with vm_lock to vm_refcnt conversion [1]. > This patchset avoids allocating additional vm_lock structure on each mmap > syscall and uses TYPESAFE_BY_RCU for vm_area_struct cache. > > 3. Sheaves used for maple tree nodes and for vm_area_struct cache with vm_lock > to vm_refcnt conversion [1]. For the vm_area_struct cache I had to replace > TYPESAFE_BY_RCU with sheaves, as we can't use both for the same cache. Hm why we can't use both? I don't think any kmem_cache_create check makes them exclusive? TYPESAFE_BY_RCU only affects how slab pages are freed, it doesn't e.g. delay reuse of individual objects, and caching in a sheaf doesn't write to the object. Am I missing something? > The values represent the total time it took to perform mmap syscalls, less is > better. > > (1) baseline control > Little core 7.58327 6.614939 (-12.77%) > Medium core 2.125315 1.428702 (-32.78%) > Big core 0.514673 0.422948 (-17.82%) > > (2) baseline control > Little core 7.58327 5.141478 (-32.20%) > Medium core 2.125315 0.427692 (-79.88%) > Big core 0.514673 0.046642 (-90.94%) > > (3) baseline control > Little core 7.58327 4.779624 (-36.97%) > Medium core 2.125315 0.450368 (-78.81%) > Big core 0.514673 0.037776 (-92.66%) > > Results in (3) vs (2) indicate that using sheaves for vm_area_struct > yields slightly better averages and I noticed that this was mostly due > to sheaves results missing occasional spikes that worsened > TYPESAFE_BY_RCU averages (the results seemed more stable with > sheaves). Thanks a lot, that looks promising! > [1] https://lore.kernel.org/all/20250213224655.1680278-1-surenb@xxxxxxxxxx/ >
