[PATCH v2 0/2] net: Optimize the qed* allocations inside kdump kernel

[PATCH v2 0/2] net: Optimize the qed* allocations inside kdump kernel

[Bhupesh Sharma]

Changes since v1:
----------------
- v1 can be seen here: http://lists.infradead.org/pipermail/kexec/2020-May/024935.html
- Addressed review comments received on v1:
  * Removed unnecessary paranthesis.
  * Used a different macro for minimum RX/TX ring count value in kdump
    kernel.

Since kdump kernel(s) run under severe memory constraint with the
basic idea being to save the crashdump vmcore reliably when the primary
kernel panics/hangs, large memory allocations done by a network driver
can cause the crashkernel to panic with OOM.

The qed* drivers take up approximately 214MB memory when run in the
kdump kernel with the default configuration settings presently used in
the driver. With an usual crashkernel size of 512M, this allocation
is equal to almost half of the total crashkernel size allocated.

See some logs obtained via memstrack tool (see [1]) below:
 dracut-pre-pivot[676]: ======== Report format module_summary: ========
 dracut-pre-pivot[676]: Module qed using 149.6MB (2394 pages), peak allocation 149.6MB (2394 pages)
 dracut-pre-pivot[676]: Module qede using 65.3MB (1045 pages), peak allocation 65.3MB (1045 pages)

This patchset tries to reduce the overall memory allocation profile of
the qed* driver when they run in the kdump kernel. With these
optimization we can see a saving of approx 85M in the kdump kernel:
 dracut-pre-pivot[671]: ======== Report format module_summary: ========
 dracut-pre-pivot[671]: Module qed using 124.6MB (1993 pages), peak allocation 124.7MB (1995 pages)
 <..snip..>
 dracut-pre-pivot[671]: Module qede using 4.6MB (73 pages), peak allocation 4.6MB (74 pages)

And the kdump kernel can save vmcore successfully via both ssh and nfs
interfaces.

This patchset contains two patches:
[PATCH 1/2] - Reduces the default TX and RX ring count in kdump kernel.
[PATCH 2/2] - Disables qed SRIOV feature in kdump kernel (as it is
              normally not a supported kdump target for saving
	      vmcore).

[1]. Memstrack tool: https://github.com/ryncsn/memstrack

Bhupesh Sharma (2):
  net: qed*: Reduce RX and TX default ring count when running inside
    kdump kernel
  net: qed: Disable SRIOV functionality inside kdump kernel

 drivers/net/ethernet/qlogic/qed/qed_sriov.h  | 10 +++++++---
 drivers/net/ethernet/qlogic/qede/qede.h      |  2 ++
 drivers/net/ethernet/qlogic/qede/qede_main.c | 13 ++++++++++---
 3 files changed, 19 insertions(+), 6 deletions(-)

-- 
2.7.4

[PATCH v2 1/2] net: qed*: Reduce RX and TX default ring count when running inside kdump kernel

[Bhupesh Sharma]

Normally kdump kernel(s) run under severe memory constraint with the
basic idea being to save the crashdump vmcore reliably when the primary
kernel panics/hangs.

Currently the qed* ethernet driver ends up consuming a lot of memory in
the kdump kernel, leading to kdump kernel panic when one tries to save
the vmcore via ssh/nfs (thus utilizing the services of the underlying
qed* network interfaces).

An example OOM message log seen in the kdump kernel can be seen here
[1], with crashkernel size reservation of 512M.

Using tools like memstrack (see [2]), we can track the modules taking up
the bulk of memory in the kdump kernel and organize the memory usage
output as per 'highest allocator first'. An example log for the OOM case
indicates that the qed* modules end up allocating approximately 216M
memory, which is a large part of the total crashkernel size:

 dracut-pre-pivot[676]: ======== Report format module_summary: ========
 dracut-pre-pivot[676]: Module qed using 149.6MB (2394 pages), peak allocation 149.6MB (2394 pages)
 dracut-pre-pivot[676]: Module qede using 65.3MB (1045 pages), peak allocation 65.3MB (1045 pages)

This patch reduces the default RX and TX ring count from 1024 to 64
when running inside kdump kernel, which leads to a significant memory
saving.

An example log with the patch applied shows the reduced memory
allocation in the kdump kernel:
 dracut-pre-pivot[674]: ======== Report format module_summary: ========
 dracut-pre-pivot[674]: Module qed using 141.8MB (2268 pages), peak allocation 141.8MB (2268 pages)
 <..snip..>
[dracut-pre-pivot[674]: Module qede using 4.8MB (76 pages), peak allocation 4.9MB (78 pages)

Tested crashdump vmcore save via ssh/nfs protocol using underlying qed*
network interface after applying this patch.

[1] OOM log:
------------

 kworker/0:6: page allocation failure: order:6,
 mode:0x60c0c0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null)
 kworker/0:6 cpuset=/ mems_allowed=0
 CPU: 0 PID: 145 Comm: kworker/0:6 Not tainted 4.18.0-109.el8.aarch64 #1
 Hardware name: To be filled by O.E.M. Saber/Saber, BIOS 0ACKL025
 01/18/2019
 Workqueue: events work_for_cpu_fn
 Call trace:
  dump_backtrace+0x0/0x188
  show_stack+0x24/0x30
  dump_stack+0x90/0xb4
  warn_alloc+0xf4/0x178
  __alloc_pages_nodemask+0xcac/0xd58
  alloc_pages_current+0x8c/0xf8
  kmalloc_order_trace+0x38/0x108
  qed_iov_alloc+0x40/0x248 [qed]
  qed_resc_alloc+0x224/0x518 [qed]
  qed_slowpath_start+0x254/0x928 [qed]
   __qede_probe+0xf8/0x5e0 [qede]
  qede_probe+0x68/0xd8 [qede]
  local_pci_probe+0x44/0xa8
  work_for_cpu_fn+0x20/0x30
  process_one_work+0x1ac/0x3e8
  worker_thread+0x44/0x448
  kthread+0x130/0x138
  ret_from_fork+0x10/0x18
  Cannot start slowpath
  qede: probe of 0000:05:00.1 failed with error -12

[2]. Memstrack tool: https://github.com/ryncsn/memstrack

Cc: kexec@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: Ariel Elior <aelior@marvell.com>
Cc: GR-everest-linux-l2@marvell.com
Cc: Manish Chopra <manishc@marvell.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
---
 drivers/net/ethernet/qlogic/qede/qede.h      |  2 ++
 drivers/net/ethernet/qlogic/qede/qede_main.c | 11 +++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qede/qede.h b/drivers/net/ethernet/qlogic/qede/qede.h
index 234c6f30effb..234c7e35ee1e 100644
--- a/drivers/net/ethernet/qlogic/qede/qede.h
+++ b/drivers/net/ethernet/qlogic/qede/qede.h
@@ -574,12 +574,14 @@ int qede_add_tc_flower_fltr(struct qede_dev *edev, __be16 proto,
 #define RX_RING_SIZE		((u16)BIT(RX_RING_SIZE_POW))
 #define NUM_RX_BDS_MAX		(RX_RING_SIZE - 1)
 #define NUM_RX_BDS_MIN		128
+#define NUM_RX_BDS_KDUMP_MIN	63
 #define NUM_RX_BDS_DEF		((u16)BIT(10) - 1)
 
 #define TX_RING_SIZE_POW	13
 #define TX_RING_SIZE		((u16)BIT(TX_RING_SIZE_POW))
 #define NUM_TX_BDS_MAX		(TX_RING_SIZE - 1)
 #define NUM_TX_BDS_MIN		128
+#define NUM_TX_BDS_KDUMP_MIN	63
 #define NUM_TX_BDS_DEF		NUM_TX_BDS_MAX
 
 #define QEDE_MIN_PKT_LEN		64
diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c b/drivers/net/ethernet/qlogic/qede/qede_main.c
index 34fa3917eb33..1a83d1fd8ccd 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_main.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_main.c
@@ -29,6 +29,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+#include <linux/crash_dump.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/version.h>
@@ -707,8 +708,14 @@ static struct qede_dev *qede_alloc_etherdev(struct qed_dev *cdev,
 	edev->dp_module = dp_module;
 	edev->dp_level = dp_level;
 	edev->ops = qed_ops;
-	edev->q_num_rx_buffers = NUM_RX_BDS_DEF;
-	edev->q_num_tx_buffers = NUM_TX_BDS_DEF;
+
+	if (is_kdump_kernel()) {
+		edev->q_num_rx_buffers = NUM_RX_BDS_KDUMP_MIN;
+		edev->q_num_tx_buffers = NUM_TX_BDS_KDUMP_MIN;
+	} else {
+		edev->q_num_rx_buffers = NUM_RX_BDS_DEF;
+		edev->q_num_tx_buffers = NUM_TX_BDS_DEF;
+	}
 
 	DP_INFO(edev, "Allocated netdev with %d tx queues and %d rx queues\n",
 		info->num_queues, info->num_queues);
-- 
2.7.4

[PATCH v2 2/2] net: qed: Disable SRIOV functionality inside kdump kernel

[Bhupesh Sharma]

Since we have kdump kernel(s) running under severe memory constraint
it makes sense to disable the qed SRIOV functionality when running the
kdump kernel as kdump configurations on several distributions don't
support SRIOV targets for saving the vmcore (see [1] for example).

Currently the qed SRIOV functionality ends up consuming memory in
the kdump kernel, when we don't really use the same.

An example log seen in the kdump kernel with the SRIOV functionality
enabled can be seen below (obtained via memstrack tool, see [2]):
 dracut-pre-pivot[676]: ======== Report format module_summary: ========
 dracut-pre-pivot[676]: Module qed using 149.6MB (2394 pages), peak allocation 149.6MB (2394 pages)

This patch disables the SRIOV functionality inside kdump kernel and with
the same applied the memory consumption goes down:
 dracut-pre-pivot[671]: ======== Report format module_summary: ========
 dracut-pre-pivot[671]: Module qed using 124.6MB (1993 pages), peak allocation 124.7MB (1995 pages)

[1]. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_monitoring_and_updating_the_kernel/installing-and-configuring-kdump_managing-monitoring-and-updating-the-kernel#supported-kdump-targets_supported-kdump-configurations-and-targets
[2]. Memstrack tool: https://github.com/ryncsn/memstrack

Cc: kexec@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: Ariel Elior <aelior@marvell.com>
Cc: GR-everest-linux-l2@marvell.com
Cc: Manish Chopra <manishc@marvell.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
---
 drivers/net/ethernet/qlogic/qed/qed_sriov.h  | 10 +++++++---
 drivers/net/ethernet/qlogic/qede/qede_main.c |  2 +-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qed/qed_sriov.h b/drivers/net/ethernet/qlogic/qed/qed_sriov.h
index 368e88565783..aabeaf03135e 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_sriov.h
+++ b/drivers/net/ethernet/qlogic/qed/qed_sriov.h
@@ -32,6 +32,7 @@
 
 #ifndef _QED_SRIOV_H
 #define _QED_SRIOV_H
+#include <linux/crash_dump.h>
 #include <linux/types.h>
 #include "qed_vf.h"
 
@@ -40,9 +41,12 @@
 #define QED_VF_ARRAY_LENGTH (3)
 
 #ifdef CONFIG_QED_SRIOV
-#define IS_VF(cdev)             ((cdev)->b_is_vf)
-#define IS_PF(cdev)             (!((cdev)->b_is_vf))
-#define IS_PF_SRIOV(p_hwfn)     (!!((p_hwfn)->cdev->p_iov_info))
+#define IS_VF(cdev)             (is_kdump_kernel() ? \
+				 (0) : ((cdev)->b_is_vf))
+#define IS_PF(cdev)             (is_kdump_kernel() ? \
+				 (1) : !((cdev)->b_is_vf))
+#define IS_PF_SRIOV(p_hwfn)     (is_kdump_kernel() ? \
+				 (0) : !!((p_hwfn)->cdev->p_iov_info))
 #else
 #define IS_VF(cdev)             (0)
 #define IS_PF(cdev)             (1)
diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c b/drivers/net/ethernet/qlogic/qede/qede_main.c
index 1a83d1fd8ccd..28afa0c49fe8 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_main.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_main.c
@@ -1194,7 +1194,7 @@ static int qede_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	case QEDE_PRIVATE_VF:
 		if (debug & QED_LOG_VERBOSE_MASK)
 			dev_err(&pdev->dev, "Probing a VF\n");
-		is_vf = true;
+		is_vf = is_kdump_kernel() ? false : true;
 		break;
 	default:
 		if (debug & QED_LOG_VERBOSE_MASK)
-- 
2.7.4

Re: [PATCH v2 0/2] net: Optimize the qed* allocations inside kdump kernel

[David Miller]

From: Bhupesh Sharma <bhsharma@redhat.com>
Date: Mon, 11 May 2020 15:41:40 +0530

 ...
> Since kdump kernel(s) run under severe memory constraint with the
> basic idea being to save the crashdump vmcore reliably when the primary
> kernel panics/hangs, large memory allocations done by a network driver
> can cause the crashkernel to panic with OOM.
> 
> The qed* drivers take up approximately 214MB memory when run in the
> kdump kernel with the default configuration settings presently used in
> the driver. With an usual crashkernel size of 512M, this allocation
> is equal to almost half of the total crashkernel size allocated.
> 
> See some logs obtained via memstrack tool (see [1]) below:
>  dracut-pre-pivot[676]: ======== Report format module_summary: ========
>  dracut-pre-pivot[676]: Module qed using 149.6MB (2394 pages), peak allocation 149.6MB (2394 pages)
>  dracut-pre-pivot[676]: Module qede using 65.3MB (1045 pages), peak allocation 65.3MB (1045 pages)
> 
> This patchset tries to reduce the overall memory allocation profile of
> the qed* driver when they run in the kdump kernel. With these
> optimization we can see a saving of approx 85M in the kdump kernel:
>  dracut-pre-pivot[671]: ======== Report format module_summary: ========
>  dracut-pre-pivot[671]: Module qed using 124.6MB (1993 pages), peak allocation 124.7MB (1995 pages)
>  <..snip..>
>  dracut-pre-pivot[671]: Module qede using 4.6MB (73 pages), peak allocation 4.6MB (74 pages)
 ...

Series applied to net-next, thanks.