Commit a5df5e79 authored by Keith Busch's avatar Keith Busch Committed by Christoph Hellwig
Browse files

nvme: allow user toggling hmb usage 



The NVMe host memory buffer may consume a non-negligable amount of
memory. Controllers are required to function without the host memory
buffer enabled, but with possibly degraded performance. Export a sysfs
property to toggle this feature on a per-device granularity so users may
choose to reclaim memory at the expense of storage performance.

Signed-off-by: default avatarKeith Busch <kbusch@kernel.org>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent e5ad96f3

drivers/nvme/host/pci.c

+44 −1
Original line number Diff line number Diff line
@@ -137,6 +137,7 @@ struct nvme_dev { 
	u32 cmbloc;

	struct nvme_ctrl ctrl;

	u32 last_ps;

	bool hmb;



	mempool_t *iod_mempool;
@@ -1896,7 +1897,9 @@ static int nvme_set_host_mem(struct nvme_dev *dev, u32 bits) 
		dev_warn(dev->ctrl.device,

			 "failed to set host mem (err %d, flags %#x).\n",

			 ret, bits);

	}

	} else

		dev->hmb = bits & NVME_HOST_MEM_ENABLE;



	return ret;

}
@@ -2081,6 +2084,42 @@ static ssize_t cmbsz_show(struct device *dev, struct device_attribute *attr, 
}

static DEVICE_ATTR_RO(cmbsz);



static ssize_t hmb_show(struct device *dev, struct device_attribute *attr,

			char *buf)

{

	struct nvme_dev *ndev = to_nvme_dev(dev_get_drvdata(dev));



	return sysfs_emit(buf, "%d\n", ndev->hmb);

}



static ssize_t hmb_store(struct device *dev, struct device_attribute *attr,

			 const char *buf, size_t count)

{

	struct nvme_dev *ndev = to_nvme_dev(dev_get_drvdata(dev));

	bool new;

	int ret;



	if (strtobool(buf, &new) < 0)

		return -EINVAL;



	if (new == ndev->hmb)

		return count;



	if (new) {

		ret = nvme_setup_host_mem(ndev);

	} else {

		ret = nvme_set_host_mem(ndev, 0);

		if (!ret)

			nvme_free_host_mem(ndev);

	}



	if (ret < 0)

		return ret;



	return count;

}

static DEVICE_ATTR_RW(hmb);



static umode_t nvme_pci_attrs_are_visible(struct kobject *kobj,

		struct attribute *a, int n)

{
@@ -2094,6 +2133,9 @@ static umode_t nvme_pci_attrs_are_visible(struct kobject *kobj, 
	    	if (!dev->cmbsz)

			return 0;

	}

	if (a == &dev_attr_hmb.attr && !ctrl->hmpre)

		return 0;



	return a->mode;

}
@@ -2101,6 +2143,7 @@ static struct attribute *nvme_pci_attrs[] = { 
	&dev_attr_cmb.attr,

	&dev_attr_cmbloc.attr,

	&dev_attr_cmbsz.attr,

	&dev_attr_hmb.attr,

	NULL,

};