[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20250905-isolcpus-io-queues-v8-11-885984c5daca@kernel.org>
Date: Fri, 05 Sep 2025 16:59:57 +0200
From: Daniel Wagner <wagi@...nel.org>
To: Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
"Michael S. Tsirkin" <mst@...hat.com>
Cc: Aaron Tomlin <atomlin@...mlin.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Costa Shulyupin <costa.shul@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
Valentin Schneider <vschneid@...hat.com>, Waiman Long <llong@...hat.com>,
Ming Lei <ming.lei@...hat.com>, Frederic Weisbecker <frederic@...nel.org>,
Mel Gorman <mgorman@...e.de>, Hannes Reinecke <hare@...e.de>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Aaron Tomlin <atomlin@...mlin.com>, linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org,
megaraidlinux.pdl@...adcom.com, linux-scsi@...r.kernel.org,
storagedev@...rochip.com, virtualization@...ts.linux.dev,
GR-QLogic-Storage-Upstream@...vell.com, Daniel Wagner <wagi@...nel.org>
Subject: [PATCH v8 11/12] blk-mq: prevent offlining hk CPUs with associated
online isolated CPUs
When isolcpus=io_queue is enabled, and the last housekeeping CPU for a
given hctx goes offline, there would be no CPU left to handle I/O. To
prevent I/O stalls, prevent offlining housekeeping CPUs that are still
serving isolated CPUs.
When isolcpus=io_queue is enabled and the last housekeeping CPU
for a given hctx goes offline, no CPU would be left to handle I/O.
To prevent I/O stalls, disallow offlining housekeeping CPUs that are
still serving isolated CPUs.
Reviewed-by: Aaron Tomlin <atomlin@...mlin.com>
Reviewed-by: Hannes Reinecke <hare@...e.de>
Signed-off-by: Daniel Wagner <wagi@...nel.org>
---
block/blk-mq.c | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index ba3a4b77f5786e5372adce53e4fff5aa2ace24aa..d48be77919e671a81077f7042103699a80959664 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3683,6 +3683,43 @@ static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx)
return data.has_rq;
}
+static bool blk_mq_hctx_can_offline_hk_cpu(struct blk_mq_hw_ctx *hctx,
+ unsigned int this_cpu)
+{
+ const struct cpumask *hk_mask = housekeeping_cpumask(HK_TYPE_IO_QUEUE);
+
+ for (int i = 0; i < hctx->nr_ctx; i++) {
+ struct blk_mq_ctx *ctx = hctx->ctxs[i];
+
+ if (ctx->cpu == this_cpu)
+ continue;
+
+ /*
+ * Check if this context has at least one online
+ * housekeeping CPU; in this case the hardware context is
+ * usable.
+ */
+ if (cpumask_test_cpu(ctx->cpu, hk_mask) &&
+ cpu_online(ctx->cpu))
+ break;
+
+ /*
+ * The context doesn't have any online housekeeping CPUs,
+ * but there might be an online isolated CPU mapped to
+ * it.
+ */
+ if (cpu_is_offline(ctx->cpu))
+ continue;
+
+ pr_warn("%s: trying to offline hctx%d but there is still an online isolcpu CPU %d mapped to it\n",
+ hctx->queue->disk->disk_name,
+ hctx->queue_num, ctx->cpu);
+ return false;
+ }
+
+ return true;
+}
+
static bool blk_mq_hctx_has_online_cpu(struct blk_mq_hw_ctx *hctx,
unsigned int this_cpu)
{
@@ -3714,6 +3751,11 @@ static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
struct blk_mq_hw_ctx, cpuhp_online);
+ if (housekeeping_enabled(HK_TYPE_IO_QUEUE)) {
+ if (!blk_mq_hctx_can_offline_hk_cpu(hctx, cpu))
+ return -EINVAL;
+ }
+
if (blk_mq_hctx_has_online_cpu(hctx, cpu))
return 0;
--
2.51.0
Powered by blists - more mailing lists