From mboxrd@z Thu Jan  1 00:00:00 1970
From: sagig@dev.mellanox.co.il (Sagi Grimberg)
Date: Sun, 7 Feb 2016 17:41:16 +0200
Subject: [RFC PATCH] dm: fix excessive dm-mq context switching
In-Reply-To: <20160205191909.GA25982@redhat.com>
References: <20160129233504.GA13661@redhat.com> <56AC79D0.5060104@suse.de>
 <20160130191238.GA18686@redhat.com> <56AEFF63.7050606@suse.de>
 <20160203180406.GA11591@redhat.com> <20160203182423.GA12913@redhat.com>
 <56B2F5BC.1010700@suse.de> <20160204135420.GA18227@redhat.com>
 <20160205151334.GA82754@redhat.com> <20160205180515.GA25808@redhat.com>
 <20160205191909.GA25982@redhat.com>
Message-ID: <56B7659C.8040601@dev.mellanox.co.il>


> FYI, here is the latest revised patch:
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.6&id=a5b835282422ec41991c1dbdb88daa4af7d166d2
>
> (revised patch header and fixed a thinko in the dm.c:rq_completed()
> change from the RFC patch I posted earlier)

Hi Mike,

So I gave your patches a go (dm-4.6) but I still don't see the
improvement you reported (while I do see a minor improvement).

null_blk queue_mode=2 submit_queues=24
dm_mod blk_mq_nr_hw_queues=24 blk_mq_queue_depth=4096 use_blk_mq=Y

I see 620K IOPs on dm_mq vs. 1750K IOPs on raw nullb0.

Is there something I'm missing?

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sagi Grimberg <sagig@dev.mellanox.co.il>
Subject: Re: [RFC PATCH] dm: fix excessive dm-mq context switching
Date: Sun, 7 Feb 2016 17:41:16 +0200
Message-ID: <56B7659C.8040601@dev.mellanox.co.il>
References: <20160129233504.GA13661@redhat.com> <56AC79D0.5060104@suse.de>
	<20160130191238.GA18686@redhat.com> <56AEFF63.7050606@suse.de>
	<20160203180406.GA11591@redhat.com> <20160203182423.GA12913@redhat.com>
	<56B2F5BC.1010700@suse.de> <20160204135420.GA18227@redhat.com>
	<20160205151334.GA82754@redhat.com> <20160205180515.GA25808@redhat.com>
	<20160205191909.GA25982@redhat.com>
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> FYI, here is the latest revised patch:
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.6&id=a5b835282422ec41991c1dbdb88daa4af7d166d2
>
> (revised patch header and fixed a thinko in the dm.c:rq_completed()
> change from the RFC patch I posted earlier)

Hi Mike,

So I gave your patches a go (dm-4.6) but I still don't see the
improvement you reported (while I do see a minor improvement).

null_blk queue_mode=2 submit_queues=24
dm_mod blk_mq_nr_hw_queues=24 blk_mq_queue_depth=4096 use_blk_mq=Y

I see 620K IOPs on dm_mq vs. 1750K IOPs on raw nullb0.

Is there something I'm missing?