From: Christoph Hellwig <hch@infradead.org>
To: Mike Christie <michael.christie@oracle.com>
Cc: Chaitanya.Kulkarni@wdc.com, loberman@redhat.com,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
target-devel@vger.kernel.org, mst@redhat.com,
stefanha@redhat.com, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 11/13] target: replace work per cmd in completion path
Date: Wed, 10 Feb 2021 08:42:41 +0000 [thread overview]
Message-ID: <20210210084241.GE2045726@infradead.org> (raw)
In-Reply-To: <20210209123845.4856-12-michael.christie@oracle.com>
On Tue, Feb 09, 2021 at 06:38:43AM -0600, Mike Christie wrote:
> Doing a work per cmd can lead to lots of threads being created.
> This patch just replaces the completion work per cmd with a per cpu
> list. Combined with the first patches this allows tcm loop on top of
> initiators like iser to go from around 700K IOPs to 1000K and reduces
> the number of threads that get created when the system is under heavy
> load and hitting the initiator drivers tagging limits.
OTOH it does increase completion latency, which might be the preference
for some workloads. Do we need a tunable here?
> +static void target_queue_cmd_work(struct se_cmd_queue *q, struct se_cmd *se_cmd,
> + int cpu, struct workqueue_struct *wq)
> {
> - struct se_cmd *cmd = container_of(work, struct se_cmd, work);
> + llist_add(&se_cmd->se_cmd_list, &q->cmd_list);
> + queue_work_on(cpu, wq, &q->work);
> +}
Do we need this helper at all? Having it open coded in the two callers
would seem easier to follow to me.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Mike Christie <michael.christie@oracle.com>
Cc: loberman@redhat.com, Chaitanya.Kulkarni@wdc.com,
martin.petersen@oracle.com, mst@redhat.com,
virtualization@lists.linux-foundation.org,
target-devel@vger.kernel.org, stefanha@redhat.com,
linux-scsi@vger.kernel.org
Subject: Re: [PATCH 11/13] target: replace work per cmd in completion path
Date: Wed, 10 Feb 2021 08:42:41 +0000 [thread overview]
Message-ID: <20210210084241.GE2045726@infradead.org> (raw)
In-Reply-To: <20210209123845.4856-12-michael.christie@oracle.com>
On Tue, Feb 09, 2021 at 06:38:43AM -0600, Mike Christie wrote:
> Doing a work per cmd can lead to lots of threads being created.
> This patch just replaces the completion work per cmd with a per cpu
> list. Combined with the first patches this allows tcm loop on top of
> initiators like iser to go from around 700K IOPs to 1000K and reduces
> the number of threads that get created when the system is under heavy
> load and hitting the initiator drivers tagging limits.
OTOH it does increase completion latency, which might be the preference
for some workloads. Do we need a tunable here?
> +static void target_queue_cmd_work(struct se_cmd_queue *q, struct se_cmd *se_cmd,
> + int cpu, struct workqueue_struct *wq)
> {
> - struct se_cmd *cmd = container_of(work, struct se_cmd, work);
> + llist_add(&se_cmd->se_cmd_list, &q->cmd_list);
> + queue_work_on(cpu, wq, &q->work);
> +}
Do we need this helper at all? Having it open coded in the two callers
would seem easier to follow to me.
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next prev parent reply other threads:[~2021-02-10 8:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 12:38 [PATCH 00/12 V2] target: fix cmd plugging and completion Mike Christie
2021-02-09 12:38 ` [PATCH 01/13] target: move t_task_cdb initialization Mike Christie
2021-02-10 8:35 ` Christoph Hellwig
2021-02-10 8:35 ` Christoph Hellwig
2021-02-09 12:38 ` [PATCH 02/13] target: split target_submit_cmd_map_sgls Mike Christie
2021-02-09 16:15 ` kernel test robot
2021-02-09 16:15 ` kernel test robot
2021-02-09 16:15 ` kernel test robot
2021-02-09 18:40 ` Mike Christie
2021-02-09 18:40 ` Mike Christie
2021-02-10 8:36 ` Christoph Hellwig
2021-02-10 8:36 ` Christoph Hellwig
2021-02-09 12:38 ` [PATCH 03/13] target: add workqueue based cmd submission Mike Christie
2021-02-09 15:48 ` Bodo Stroesser
2021-02-09 18:43 ` Mike Christie
2021-02-09 19:10 ` Mike Christie
2021-02-09 12:38 ` [PATCH 04/13] vhost scsi: use lio wq cmd submission helper Mike Christie
2021-02-09 12:38 ` [PATCH 05/13] tcm loop: use blk cmd allocator for se_cmds Mike Christie
2021-02-10 8:37 ` Christoph Hellwig
2021-02-10 8:37 ` Christoph Hellwig
2021-02-09 12:38 ` [PATCH 06/13] tcm loop: use lio wq cmd submission helper Mike Christie
2021-02-09 15:59 ` Bodo Stroesser
2021-02-09 18:44 ` Mike Christie
2021-02-09 17:39 ` kernel test robot
2021-02-09 17:39 ` kernel test robot
2021-02-09 12:38 ` [PATCH 07/13] target: cleanup cmd flag bits Mike Christie
2021-02-10 8:38 ` Christoph Hellwig
2021-02-10 8:38 ` Christoph Hellwig
2021-02-09 12:38 ` [PATCH 08/13] target: fix backend plugging Mike Christie
2021-02-09 12:38 ` [PATCH 09/13] target iblock: add backend plug/unplug callouts Mike Christie
2021-02-09 12:38 ` [PATCH 10/13] target_core_user: " Mike Christie
2021-02-09 16:32 ` Bodo Stroesser
2021-02-09 18:59 ` Mike Christie
2021-02-09 12:38 ` [PATCH 11/13] target: replace work per cmd in completion path Mike Christie
2021-02-09 17:01 ` Bodo Stroesser
2021-02-09 18:50 ` Mike Christie
2021-02-10 8:42 ` Christoph Hellwig [this message]
2021-02-10 8:42 ` Christoph Hellwig
2021-02-10 18:33 ` Mike Christie
2021-02-09 12:38 ` [PATCH 12/13] target, vhost-scsi: don't switch cpus on completion Mike Christie
2021-02-10 8:44 ` Christoph Hellwig
2021-02-10 8:44 ` Christoph Hellwig
2021-02-10 18:43 ` Mike Christie
2021-02-10 18:45 ` Mike Christie
2021-02-09 12:38 ` [PATCH 13/13] target: flush submission work during TMR processing Mike Christie
2021-02-09 14:31 ` Laurence Oberman
2021-02-10 14:25 ` Laurence Oberman
2021-02-09 17:05 ` Bodo Stroesser
2021-02-09 18:49 ` Mike Christie
2021-02-10 4:55 [PATCH 00/13 V3] target: fix cmd plugging and completion Mike Christie
2021-02-10 4:55 ` [PATCH 11/13] target: replace work per cmd in completion path Mike Christie
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