Commit bcff0888 authored by Jim Harris's avatar Jim Harris Committed by Tomasz Zawadzki
Browse files

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



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: default avatarJim 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: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarTomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: default avatarBen Walker <benjamin.walker@intel.com>
parent f1acee8f

module/scheduler/dynamic/scheduler_dynamic.c

+19 −0
Original line number Diff line number Diff line
@@ -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--;

test/unit/lib/event/reactor.c/reactor_ut.c

+1 −5
Original line number Diff line number Diff line
@@ -729,12 +729,8 @@ 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));

	}

	}



	g_reactor_state = SPDK_REACTOR_STATE_INITIALIZED;