[PATCH] nvmet: dynamically allocate nvmet_ns->nguid
Chaitanya Kulkarni
kch at nvidia.com
Mon May 1 22:30:51 PDT 2023
The nvmet_ns struct is critical to I/O operations in each backend bdev
and file, but its static nguid array is not accessed in the fast path.
This means that pulling all the memory for the array on each access
is inefficient.
This patch dynamically allocates the nvmet_ns->nguid array, reducing the
size of the nvmet_ns struct. This optimization should reduce unnecessary
memory access in the fast path that is required for the array vs pointer.
For allocation of nguid with kzalloc() use same policy GFP_KERNEL that is
used to allocate nvmet_ns struct iself.
struct nvmet_ns size difference with pahole :-
with this patch :- /* size: 440, cachelines: 7, members: 23 */
without this patch :- /* size: 448, cachelines: 7, members: 23 */
Signed-off-by: Chaitanya Kulkarni <kch at nvidia.com>
---
Following is the difference with pahole:
With this patch :-
struct nvmet_ns {
struct percpu_ref ref; /* 0 16 */
struct block_device * bdev; /* 16 8 */
struct file * file; /* 24 8 */
bool readonly; /* 32 1 */
/* XXX 3 bytes hole, try to pack */
u32 nsid; /* 36 4 */
u32 blksize_shift; /* 40 4 */
/* XXX 4 bytes hole, try to pack */
loff_t size; /* 48 8 */
u8 * nguid; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */
uuid_t uuid; /* 64 16 */
u32 anagrpid; /* 80 4 */
bool buffered_io; /* 84 1 */
bool enabled; /* 85 1 */
/* XXX 2 bytes hole, try to pack */
struct nvmet_subsys * subsys; /* 88 8 */
const char * device_path; /* 96 8 */
struct config_group device_group; /* 104 136 */
/* --- cacheline 3 boundary (192 bytes) was 48 bytes ago --- */
struct config_group group; /* 240 136 */
/* --- cacheline 5 boundary (320 bytes) was 56 bytes ago --- */
struct completion disable_done; /* 376 32 */
/* --- cacheline 6 boundary (384 bytes) was 24 bytes ago --- */
mempool_t * bvec_pool; /* 408 8 */
struct pci_dev * p2p_dev; /* 416 8 */
int use_p2pmem; /* 424 4 */
int pi_type; /* 428 4 */
int metadata_size; /* 432 4 */
u8 csi; /* 436 1 */
/* size: 440, cachelines: 7, members: 23 */
/* sum members: 428, holes: 3, sum holes: 9 */
/* padding: 3 */
/* last cacheline: 56 bytes */
};
Without this patch :-
struct nvmet_ns {
struct percpu_ref ref; /* 0 16 */
struct block_device * bdev; /* 16 8 */
struct file * file; /* 24 8 */
bool readonly; /* 32 1 */
/* XXX 3 bytes hole, try to pack */
u32 nsid; /* 36 4 */
u32 blksize_shift; /* 40 4 */
/* XXX 4 bytes hole, try to pack */
loff_t size; /* 48 8 */
u8 nguid[16]; /* 56 16 */
/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
uuid_t uuid; /* 72 16 */
u32 anagrpid; /* 88 4 */
bool buffered_io; /* 92 1 */
bool enabled; /* 93 1 */
/* XXX 2 bytes hole, try to pack */
struct nvmet_subsys * subsys; /* 96 8 */
const char * device_path; /* 104 8 */
struct config_group device_group; /* 112 136 */
/* --- cacheline 3 boundary (192 bytes) was 56 bytes ago --- */
struct config_group group; /* 248 136 */
/* --- cacheline 6 boundary (384 bytes) --- */
struct completion disable_done; /* 384 32 */
mempool_t * bvec_pool; /* 416 8 */
struct pci_dev * p2p_dev; /* 424 8 */
int use_p2pmem; /* 432 4 */
int pi_type; /* 436 4 */
int metadata_size; /* 440 4 */
u8 csi; /* 444 1 */
/* size: 448, cachelines: 7, members: 23 */
/* sum members: 436, holes: 3, sum holes: 9 */
/* padding: 3 */
};
Please note that this patch is generated on the top of
("nvmet: Reorder fields in 'struct nvmet_ns'") :-
https://www.spinics.net/lists/kernel/msg4773169.html
drivers/nvme/target/admin-cmd.c | 6 +++---
drivers/nvme/target/configfs.c | 4 ++--
drivers/nvme/target/core.c | 7 +++++++
drivers/nvme/target/nvmet.h | 2 +-
4 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 39cb570f833d..21129ad15320 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -551,7 +551,7 @@ static void nvmet_execute_identify_ns(struct nvmet_req *req)
id->nmic = NVME_NS_NMIC_SHARED;
id->anagrpid = cpu_to_le32(req->ns->anagrpid);
- memcpy(&id->nguid, &req->ns->nguid, sizeof(id->nguid));
+ memcpy(&id->nguid, req->ns->nguid, sizeof(id->nguid));
id->lbaf[0].ds = req->ns->blksize_shift;
@@ -646,10 +646,10 @@ static void nvmet_execute_identify_desclist(struct nvmet_req *req)
if (status)
goto out;
}
- if (memchr_inv(req->ns->nguid, 0, sizeof(req->ns->nguid))) {
+ if (memchr_inv(req->ns->nguid, 0, NVME_NIDT_NGUID_LEN)) {
status = nvmet_copy_ns_identifier(req, NVME_NIDT_NGUID,
NVME_NIDT_NGUID_LEN,
- &req->ns->nguid, &off);
+ req->ns->nguid, &off);
if (status)
goto out;
}
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 907143870da5..463ae31d5d71 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -444,7 +444,7 @@ CONFIGFS_ATTR(nvmet_ns_, device_uuid);
static ssize_t nvmet_ns_device_nguid_show(struct config_item *item, char *page)
{
- return sprintf(page, "%pUb\n", &to_nvmet_ns(item)->nguid);
+ return sprintf(page, "%pUb\n", to_nvmet_ns(item)->nguid);
}
static ssize_t nvmet_ns_device_nguid_store(struct config_item *item,
@@ -480,7 +480,7 @@ static ssize_t nvmet_ns_device_nguid_store(struct config_item *item,
p++;
}
- memcpy(&ns->nguid, nguid, sizeof(nguid));
+ memcpy(ns->nguid, nguid, sizeof(nguid));
out_unlock:
mutex_unlock(&subsys->lock);
return ret ? ret : count;
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index f66ed13d7c11..cc95ba3c2835 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -665,6 +665,7 @@ void nvmet_ns_free(struct nvmet_ns *ns)
up_write(&nvmet_ana_sem);
kfree(ns->device_path);
+ kfree(ns->nguid);
kfree(ns);
}
@@ -676,6 +677,12 @@ struct nvmet_ns *nvmet_ns_alloc(struct nvmet_subsys *subsys, u32 nsid)
if (!ns)
return NULL;
+ ns->nguid = kzalloc(NVME_NIDT_NGUID_LEN, GFP_KERNEL);
+ if (!ns) {
+ kfree(ns);
+ return NULL;
+ }
+
init_completion(&ns->disable_done);
ns->nsid = nsid;
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index c50146085fb5..4c2a20dc9eed 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -64,7 +64,7 @@ struct nvmet_ns {
u32 nsid;
u32 blksize_shift;
loff_t size;
- u8 nguid[16];
+ u8 *nguid;
uuid_t uuid;
u32 anagrpid;
--
2.40.0
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