The branch main has been updated by imp: URL: https://cgit.FreeBSD.org/src/commit/?id=20f8814cd3fa6b7cda704e07dec4da6cb9647e37
commit 20f8814cd3fa6b7cda704e07dec4da6cb9647e37 Author: Warner Losh <[email protected]> AuthorDate: 2023-11-13 14:23:53 +0000 Commit: Warner Losh <[email protected]> CommitDate: 2023-11-13 14:23:53 +0000 busdma: On systmes that use subr_busdma_bounce, measure deferred time Measure the total deferred time (from the time we decide to defer until we try again) for busdma_load requests. On systems that don't ever defer, there is no performnce change. Add new sysctl hw.busdma.zoneX.total_deferred_time to report this (in microseconds). Normally, deferrals don't happen in modern hardware... Except there's a lot of buggy hardware that can't cope with memory > 4GB or that can't cross a 4GB boundary (or even more restrictive values), necessitating bouncing. This will measure the effect on the I/Os of this deferral. Sponsored by: Netflix Reviewed by: gallatin, mav Differential Revision: https://reviews.freebsd.org/D42550 --- sys/arm64/arm64/busdma_bounce.c | 1 + sys/kern/subr_busdma_bounce.c | 10 +++++++++- sys/riscv/riscv/busdma_bounce.c | 1 + sys/x86/x86/busdma_bounce.c | 1 + 4 files changed, 12 insertions(+), 1 deletion(-) diff --git a/sys/arm64/arm64/busdma_bounce.c b/sys/arm64/arm64/busdma_bounce.c index c1028f35ba7f..ee84d03a44d4 100644 --- a/sys/arm64/arm64/busdma_bounce.c +++ b/sys/arm64/arm64/busdma_bounce.c @@ -98,6 +98,7 @@ struct bus_dmamap { struct memdesc mem; bus_dmamap_callback_t *callback; void *callback_arg; + __sbintime_t queued_time; STAILQ_ENTRY(bus_dmamap) links; u_int flags; #define DMAMAP_COHERENT (1 << 0) diff --git a/sys/kern/subr_busdma_bounce.c b/sys/kern/subr_busdma_bounce.c index f5f27dae9b05..76f50b2abf38 100644 --- a/sys/kern/subr_busdma_bounce.c +++ b/sys/kern/subr_busdma_bounce.c @@ -76,6 +76,7 @@ struct bounce_zone { #ifdef dmat_domain int domain; #endif + sbintime_t total_deferred_time; bus_size_t alignment; bus_addr_t lowaddr; char zoneid[8]; @@ -119,6 +120,7 @@ _bus_dmamap_reserve_pages(bus_dma_tag_t dmat, bus_dmamap_t map, int flags) bz = dmat->bounce_zone; STAILQ_INSERT_TAIL(&bz->bounce_map_waitinglist, map, links); + map->queued_time = sbinuptime(); mtx_unlock(&bounce_lock); return (EINPROGRESS); } @@ -239,7 +241,10 @@ alloc_bounce_zone(bus_dma_tag_t dmat) "domain", CTLFLAG_RD, &bz->domain, 0, "memory domain"); #endif - + SYSCTL_ADD_SBINTIME_USEC(busdma_sysctl_tree(bz), + SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO, + "total_deferred_time", CTLFLAG_RD, &bz->total_deferred_time, + "Cumulative time busdma requests are deferred (us)"); if (start_thread) { if (kproc_create(busdma_thread, NULL, NULL, 0, 0, "busdma") != 0) @@ -436,6 +441,7 @@ busdma_thread(void *dummy __unused) STAILQ_HEAD(, bus_dmamap) callbacklist; bus_dma_tag_t dmat; struct bus_dmamap *map, *nmap; + struct bounce_zone *bz; thread_lock(curthread); sched_class(curthread, PRI_ITHD); @@ -452,8 +458,10 @@ busdma_thread(void *dummy __unused) STAILQ_FOREACH_SAFE(map, &callbacklist, links, nmap) { dmat = map->dmat; + bz = dmat->bounce_zone; dmat_lockfunc(dmat)(dmat_lockfuncarg(dmat), BUS_DMA_LOCK); + bz->total_deferred_time += (sbinuptime() - map->queued_time); bus_dmamap_load_mem(map->dmat, map, &map->mem, map->callback, map->callback_arg, BUS_DMA_WAITOK); dmat_lockfunc(dmat)(dmat_lockfuncarg(dmat), diff --git a/sys/riscv/riscv/busdma_bounce.c b/sys/riscv/riscv/busdma_bounce.c index 6b50dc527b66..2aa6c0d0b371 100644 --- a/sys/riscv/riscv/busdma_bounce.c +++ b/sys/riscv/riscv/busdma_bounce.c @@ -95,6 +95,7 @@ struct bus_dmamap { struct memdesc mem; bus_dmamap_callback_t *callback; void *callback_arg; + __sbintime_t queued_time; STAILQ_ENTRY(bus_dmamap) links; u_int flags; #define DMAMAP_COULD_BOUNCE (1 << 0) diff --git a/sys/x86/x86/busdma_bounce.c b/sys/x86/x86/busdma_bounce.c index b9943ad3792e..6ae02752a805 100644 --- a/sys/x86/x86/busdma_bounce.c +++ b/sys/x86/x86/busdma_bounce.c @@ -90,6 +90,7 @@ struct bus_dmamap { struct memdesc mem; bus_dmamap_callback_t *callback; void *callback_arg; + __sbintime_t queued_time; STAILQ_ENTRY(bus_dmamap) links; #ifdef KMSAN struct memdesc kmsan_mem;
