linux-kernel - Re: [External] : Re: [bug-report] 5-9% FIO randomwrite ext4 perf regression on 6.12.y kernel

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Message-ID: <20241125064658.GA14937@lst.de>
Date: Mon, 25 Nov 2024 07:46:58 +0100
From: Christoph Hellwig <hch@....de>
To: Keith Busch <kbusch@...nel.org>
Cc: Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>,
	Paul Webb <paul.x.webb@...cle.com>, Christoph Hellwig <hch@....de>,
	Jens Axboe <axboe@...nel.dk>, Phil Auld <pauld@...hat.com>,
	Chaitanya Kulkarni <chaitanyak@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
	Ramanan Govindarajan <ramanan.govindarajan@...cle.com>,
	Sagi Grimberg <sagi@...mberg.me>,
	Nicky Veitch <nicky.veitch@...cle.com>
Subject: Re: [External] : Re: [bug-report] 5-9% FIO randomwrite ext4 perf
 regression on 6.12.y kernel

On Fri, Nov 22, 2024 at 02:09:04PM -0700, Keith Busch wrote:
> Could you instead try deleting the NVME_QUIRK_DEALLOCATE_ZEROES quirk
> for this device? The driver apparently uses this to assume you meant to
> do a Discard, but it sounds like the device wants an actual Write Zeroes
> command here.

>From the logs it sounds like the device does not support the DSM command
at all.  Which is a bit weird, but might be an odd OEM firmware of some
kind.  If that's the case, the patch below should fix it:

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 1a8d32a4a5c3..ca57086ba038 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2068,7 +2068,8 @@ static bool nvme_update_disk_info(struct nvme_ns *ns, struct nvme_id_ns *id,
 	lim->physical_block_size = min(phys_bs, atomic_bs);
 	lim->io_min = phys_bs;
 	lim->io_opt = io_opt;
-	if (ns->ctrl->quirks & NVME_QUIRK_DEALLOCATE_ZEROES)
+	if ((ns->ctrl->quirks & NVME_QUIRK_DEALLOCATE_ZEROES) &&
+	    (ns->ctrl->oncs & NVME_CTRL_ONCS_DSM))
 		lim->max_write_zeroes_sectors = UINT_MAX;
 	else
 		lim->max_write_zeroes_sectors = ns->ctrl->max_zeroes_sectors;