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nvme: allow user toggling hmb usage

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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: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Keith Busch 2021-07-27 09:40:43 -07:00 committed by Christoph Hellwig
parent e5ad96f388
commit a5df5e79c4
1 changed files with 44 additions and 1 deletions
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45
drivers/nvme/host/pci.c
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@ -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,
};