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scheduler/dynamic: don't adjust tsc too much for very busy cores

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If a core has a very high busy percentage, we should
not assume that moving a thread will gain that
thread's busy tsc as newly idle cycles for the
current core.

So if the current core's percentage is above
SCHEDULER_CORE_BUSY (95%), do not adjust the
current core's busy/idle tsc when moving a thread
off of it.  If moving the thread does actually
result in some newly idle tsc, it will get adjusted
next scheduling period.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I26a0282cd8f8e821809289b80c979cf94335353d

Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/9581
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
This commit is contained in:
Jim Harris 2021-09-22 10:19:29 -07:00 committed by Tomasz Zawadzki
parent f1acee8f83
commit bcff088852
2 changed files with 20 additions and 5 deletions
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19
module/scheduler/dynamic/scheduler_dynamic.c
View File

@ -53,6 +53,7 @@ static struct core_stats *g_cores;
#define SCHEDULER_LOAD_LIMIT 20
#define SCHEDULER_CORE_LIMIT 95
#define SCHEDULER_CORE_BUSY 95
static uint8_t
_busy_pct(uint64_t busy, uint64_t idle)
@ -98,6 +99,8 @@ _move_thread(struct spdk_scheduler_thread_info *thread_info, uint32_t dst_core)
struct core_stats *dst = &g_cores[dst_core];
struct core_stats *src = &g_cores[thread_info->lcore];
uint64_t busy_tsc = thread_info->current_stats.busy_tsc;
uint8_t busy_pct = _busy_pct(src->busy, src->idle);
uint64_t tsc;
if (src == dst) {
/* Don't modify stats if thread is already on that core. */
@ -113,6 +116,22 @@ _move_thread(struct spdk_scheduler_thread_info *thread_info, uint32_t dst_core)
src->busy -= spdk_min(src->busy, busy_tsc);
src->idle += spdk_min(UINT64_MAX - src->idle, busy_tsc);
if (busy_pct >= SCHEDULER_CORE_BUSY &&
_busy_pct(src->busy, src->idle) < SCHEDULER_CORE_LIMIT) {
/* This core was so busy that we cannot assume all of busy_tsc
* consumed by the moved thread will now be idle_tsc - it's
* very possible the remaining threads will use these cycles
* as busy_tsc.
*
* So make sure we don't drop the updated estimate below
* SCHEDULER_CORE_LIMIT, so that other cores can't
* move threads to this core during this scheduling
* period.
*/
tsc = src->busy + src->idle;
src->busy = tsc * SCHEDULER_CORE_LIMIT / 100;
src->idle = tsc - src->busy;
}
assert(src->thread_count > 0);
src->thread_count--;

6
test/unit/lib/event/reactor.c/reactor_ut.c
View File

@ -729,11 +729,7 @@ test_scheduler(void)
for (i = 0; i < 3; i++) {
reactor = spdk_reactor_get(i);
CU_ASSERT(reactor != NULL);
if (i == 2) {
CU_ASSERT(TAILQ_EMPTY(&reactor->threads));
} else {
CU_ASSERT(!TAILQ_EMPTY(&reactor->threads));
}
CU_ASSERT(!TAILQ_EMPTY(&reactor->threads));
}
g_reactor_state = SPDK_REACTOR_STATE_INITIALIZED;