From: Saurabh Sengar ssengar@linux.microsoft.com
On a x86 system under test with 1780 CPUs, topology_span_sane() takes around 8 seconds cumulatively for all the iterations. It is an expensive operation which does the sanity of non-NUMA topology masks.
CPU topology is not something which changes very frequently hence make this check optional for the systems where the topology is trusted and need faster bootup.
Restrict this to sched_verbose kernel cmdline option so that this penalty can be avoided for the systems who want to avoid it.
Cc: stable@vger.kernel.org Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Co-developed-by: Naman Jain namjain@linux.microsoft.com Signed-off-by: Naman Jain namjain@linux.microsoft.com Tested-by: K Prateek Nayak kprateek.nayak@amd.com --- Changes since v4: https://lore.kernel.org/all/20250306055354.52915-1-namjain@linux.microsoft.c... - Rephrased print statement and moved it to sched_domain_debug. (addressing Valentin's comments) Changes since v3: https://lore.kernel.org/all/20250203114738.3109-1-namjain@linux.microsoft.co... - Minor typo correction in comment - Added Tested-by tag from Prateek for x86 Changes since v2: https://lore.kernel.org/all/1731922777-7121-1-git-send-email-ssengar@linux.m... - Use sched_debug() instead of using sched_debug_verbose variable directly (addressing Prateek's comment)
Changes since v1: https://lore.kernel.org/all/1729619853-2597-1-git-send-email-ssengar@linux.m... - Use kernel cmdline param instead of compile time flag.
Adding a link to the other patch which is under review. https://lore.kernel.org/lkml/20241031200431.182443-1-steve.wahl@hpe.com/ Above patch tries to optimize the topology sanity check, whereas this patch makes it optional. We believe both patches can coexist, as even with optimization, there will still be some performance overhead for this check.
--- kernel/sched/topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index c49aea8c1025..d7254c47af45 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -132,8 +132,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0;
- if (!sched_debug_verbose) + if (!sched_debug_verbose) { + pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n", + __func__); return; + }
if (!sd) { printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu); @@ -2359,6 +2362,10 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, { int i = cpu + 1;
+ /* Skip the topology sanity check for non-debug, as it is a time-consuming operation */ + if (!sched_debug()) + return true; + /* NUMA levels are allowed to overlap */ if (tl->flags & SDTL_OVERLAP) return true;
base-commit: 7ec162622e66a4ff886f8f28712ea1b13069e1aa
On 10/03/25 10:55, Naman Jain wrote:
From: Saurabh Sengar ssengar@linux.microsoft.com
On a x86 system under test with 1780 CPUs, topology_span_sane() takes around 8 seconds cumulatively for all the iterations. It is an expensive operation which does the sanity of non-NUMA topology masks.
CPU topology is not something which changes very frequently hence make this check optional for the systems where the topology is trusted and need faster bootup.
Restrict this to sched_verbose kernel cmdline option so that this penalty can be avoided for the systems who want to avoid it.
Cc: stable@vger.kernel.org Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Co-developed-by: Naman Jain namjain@linux.microsoft.com Signed-off-by: Naman Jain namjain@linux.microsoft.com Tested-by: K Prateek Nayak kprateek.nayak@amd.com
Changes since v4: https://lore.kernel.org/all/20250306055354.52915-1-namjain@linux.microsoft.c... - Rephrased print statement and moved it to sched_domain_debug. (addressing Valentin's comments) Changes since v3: https://lore.kernel.org/all/20250203114738.3109-1-namjain@linux.microsoft.co... - Minor typo correction in comment - Added Tested-by tag from Prateek for x86 Changes since v2: https://lore.kernel.org/all/1731922777-7121-1-git-send-email-ssengar@linux.m... - Use sched_debug() instead of using sched_debug_verbose variable directly (addressing Prateek's comment)
Changes since v1: https://lore.kernel.org/all/1729619853-2597-1-git-send-email-ssengar@linux.m... - Use kernel cmdline param instead of compile time flag.
Adding a link to the other patch which is under review. https://lore.kernel.org/lkml/20241031200431.182443-1-steve.wahl@hpe.com/ Above patch tries to optimize the topology sanity check, whereas this patch makes it optional. We believe both patches can coexist, as even with optimization, there will still be some performance overhead for this check.
kernel/sched/topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index c49aea8c1025..d7254c47af45 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -132,8 +132,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0;
- if (!sched_debug_verbose)
- if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",__func__); return;- }
Nit: I've been told not to break warnings over multiple lines so they can be grep'ed, but given this has the "sched_domain_debug:" prefix I think we could get away with the below.
Regardless: Reviewed-by: Valentin Schneider vschneid@redhat.com
--- diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d7254c47af455..b4dc7c7d2c41c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -133,7 +133,8 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) int level = 0;
if (!sched_debug_verbose) { - pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n", + pr_info_once("%s: Scheduler topology debugging disabled, " + "add 'sched_verbose' to the cmdline to enable it\n", __func__); return; }
On 3/11/2025 9:02 PM, Valentin Schneider wrote:
On 10/03/25 10:55, Naman Jain wrote:
From: Saurabh Sengar ssengar@linux.microsoft.com
On a x86 system under test with 1780 CPUs, topology_span_sane() takes around 8 seconds cumulatively for all the iterations. It is an expensive operation which does the sanity of non-NUMA topology masks.
CPU topology is not something which changes very frequently hence make this check optional for the systems where the topology is trusted and need faster bootup.
Restrict this to sched_verbose kernel cmdline option so that this penalty can be avoided for the systems who want to avoid it.
Cc: stable@vger.kernel.org Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Co-developed-by: Naman Jain namjain@linux.microsoft.com Signed-off-by: Naman Jain namjain@linux.microsoft.com Tested-by: K Prateek Nayak kprateek.nayak@amd.com
Changes since v4: https://lore.kernel.org/all/20250306055354.52915-1-namjain@linux.microsoft.c... - Rephrased print statement and moved it to sched_domain_debug. (addressing Valentin's comments) Changes since v3: https://lore.kernel.org/all/20250203114738.3109-1-namjain@linux.microsoft.co... - Minor typo correction in comment - Added Tested-by tag from Prateek for x86 Changes since v2: https://lore.kernel.org/all/1731922777-7121-1-git-send-email-ssengar@linux.m... - Use sched_debug() instead of using sched_debug_verbose variable directly (addressing Prateek's comment)
Changes since v1: https://lore.kernel.org/all/1729619853-2597-1-git-send-email-ssengar@linux.m... - Use kernel cmdline param instead of compile time flag.
Adding a link to the other patch which is under review. https://lore.kernel.org/lkml/20241031200431.182443-1-steve.wahl@hpe.com/ Above patch tries to optimize the topology sanity check, whereas this patch makes it optional. We believe both patches can coexist, as even with optimization, there will still be some performance overhead for this check.
kernel/sched/topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index c49aea8c1025..d7254c47af45 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -132,8 +132,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0;
- if (!sched_debug_verbose)
- if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",__func__); return;- }
Nit: I've been told not to break warnings over multiple lines so they can be grep'ed, but given this has the "sched_domain_debug:" prefix I think we could get away with the below.
Regardless: Reviewed-by: Valentin Schneider vschneid@redhat.com
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d7254c47af455..b4dc7c7d2c41c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -133,7 +133,8 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) int level = 0; if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",
pr_info_once("%s: Scheduler topology debugging disabled, ""add 'sched_verbose' to the cmdline to enable it\n", __func__);
Thanks for reviewing. I'll wait a couple more days to push the next version.
Thanks, Naman
On 3/11/2025 9:02 PM, Valentin Schneider wrote:
On 10/03/25 10:55, Naman Jain wrote:
From: Saurabh Sengar ssengar@linux.microsoft.com
On a x86 system under test with 1780 CPUs, topology_span_sane() takes around 8 seconds cumulatively for all the iterations. It is an expensive operation which does the sanity of non-NUMA topology masks.
CPU topology is not something which changes very frequently hence make this check optional for the systems where the topology is trusted and need faster bootup.
Restrict this to sched_verbose kernel cmdline option so that this penalty can be avoided for the systems who want to avoid it.
Cc: stable@vger.kernel.org Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Co-developed-by: Naman Jain namjain@linux.microsoft.com Signed-off-by: Naman Jain namjain@linux.microsoft.com Tested-by: K Prateek Nayak kprateek.nayak@amd.com
Changes since v4: https://lore.kernel.org/all/20250306055354.52915-1-namjain@linux.microsoft.c... - Rephrased print statement and moved it to sched_domain_debug. (addressing Valentin's comments) Changes since v3: https://lore.kernel.org/all/20250203114738.3109-1-namjain@linux.microsoft.co... - Minor typo correction in comment - Added Tested-by tag from Prateek for x86 Changes since v2: https://lore.kernel.org/all/1731922777-7121-1-git-send-email-ssengar@linux.m... - Use sched_debug() instead of using sched_debug_verbose variable directly (addressing Prateek's comment)
Changes since v1: https://lore.kernel.org/all/1729619853-2597-1-git-send-email-ssengar@linux.m... - Use kernel cmdline param instead of compile time flag.
Adding a link to the other patch which is under review. https://lore.kernel.org/lkml/20241031200431.182443-1-steve.wahl@hpe.com/ Above patch tries to optimize the topology sanity check, whereas this patch makes it optional. We believe both patches can coexist, as even with optimization, there will still be some performance overhead for this check.
kernel/sched/topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index c49aea8c1025..d7254c47af45 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -132,8 +132,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0;
- if (!sched_debug_verbose)
- if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",__func__); return;- }
Nit: I've been told not to break warnings over multiple lines so they can be grep'ed, but given this has the "sched_domain_debug:" prefix I think we could get away with the below.
Regardless: Reviewed-by: Valentin Schneider vschneid@redhat.com
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d7254c47af455..b4dc7c7d2c41c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -133,7 +133,8 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) int level = 0; if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",
pr_info_once("%s: Scheduler topology debugging disabled, ""add 'sched_verbose' to the cmdline to enable it\n", __func__);
Hi Valentin, Splitting the warning to different lines give checkpatch error with --strict option. --fix option suggests we keep it like we have it originally(single line). Please let me know if you feel we can change it to something else or if you are fine with picking the change for next iteration. Thanks again.
# ./scripts/checkpatch.pl --strict v6-0001-sched-topology-Enable-topology_span_sane-check-on.patch WARNING: quoted string split across lines #40: FILE: kernel/sched/topology.c:137: + pr_info_once("%s: Scheduler topology debugging disabled, " + "add 'sched_verbose' to the cmdline to enable it\n",
total: 0 errors, 1 warnings, 0 checks, 23 lines checked
Regards, Naman
On 17/03/25 15:27, Naman Jain wrote:
On 3/11/2025 9:02 PM, Valentin Schneider wrote:
On 10/03/25 10:55, Naman Jain wrote:
From: Saurabh Sengar ssengar@linux.microsoft.com
On a x86 system under test with 1780 CPUs, topology_span_sane() takes around 8 seconds cumulatively for all the iterations. It is an expensive operation which does the sanity of non-NUMA topology masks.
CPU topology is not something which changes very frequently hence make this check optional for the systems where the topology is trusted and need faster bootup.
Restrict this to sched_verbose kernel cmdline option so that this penalty can be avoided for the systems who want to avoid it.
Cc: stable@vger.kernel.org Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Co-developed-by: Naman Jain namjain@linux.microsoft.com Signed-off-by: Naman Jain namjain@linux.microsoft.com Tested-by: K Prateek Nayak kprateek.nayak@amd.com
Changes since v4: https://lore.kernel.org/all/20250306055354.52915-1-namjain@linux.microsoft.c... - Rephrased print statement and moved it to sched_domain_debug. (addressing Valentin's comments) Changes since v3: https://lore.kernel.org/all/20250203114738.3109-1-namjain@linux.microsoft.co... - Minor typo correction in comment - Added Tested-by tag from Prateek for x86 Changes since v2: https://lore.kernel.org/all/1731922777-7121-1-git-send-email-ssengar@linux.m... - Use sched_debug() instead of using sched_debug_verbose variable directly (addressing Prateek's comment)
Changes since v1: https://lore.kernel.org/all/1729619853-2597-1-git-send-email-ssengar@linux.m... - Use kernel cmdline param instead of compile time flag.
Adding a link to the other patch which is under review. https://lore.kernel.org/lkml/20241031200431.182443-1-steve.wahl@hpe.com/ Above patch tries to optimize the topology sanity check, whereas this patch makes it optional. We believe both patches can coexist, as even with optimization, there will still be some performance overhead for this check.
kernel/sched/topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index c49aea8c1025..d7254c47af45 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -132,8 +132,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0;
- if (!sched_debug_verbose)
- if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",__func__); return;- }
Nit: I've been told not to break warnings over multiple lines so they can be grep'ed, but given this has the "sched_domain_debug:" prefix I think we could get away with the below.
Regardless: Reviewed-by: Valentin Schneider vschneid@redhat.com
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d7254c47af455..b4dc7c7d2c41c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -133,7 +133,8 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) int level = 0; if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",
pr_info_once("%s: Scheduler topology debugging disabled, ""add 'sched_verbose' to the cmdline to enable it\n", __func__);Hi Valentin, Splitting the warning to different lines give checkpatch error with --strict option. --fix option suggests we keep it like we have it originally(single line). Please let me know if you feel we can change it to something else or if you are fine with picking the change for next iteration. Thanks again.
Hah, didn't know that was in checkpatch :-) As I said before that really was more of a nitpick, consider me OK with the current patch.
On 3/17/2025 3:55 PM, Valentin Schneider wrote:
On 17/03/25 15:27, Naman Jain wrote:
On 3/11/2025 9:02 PM, Valentin Schneider wrote:
On 10/03/25 10:55, Naman Jain wrote:
From: Saurabh Sengar ssengar@linux.microsoft.com
On a x86 system under test with 1780 CPUs, topology_span_sane() takes around 8 seconds cumulatively for all the iterations. It is an expensive operation which does the sanity of non-NUMA topology masks.
CPU topology is not something which changes very frequently hence make this check optional for the systems where the topology is trusted and need faster bootup.
Restrict this to sched_verbose kernel cmdline option so that this penalty can be avoided for the systems who want to avoid it.
Cc: stable@vger.kernel.org Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Co-developed-by: Naman Jain namjain@linux.microsoft.com Signed-off-by: Naman Jain namjain@linux.microsoft.com Tested-by: K Prateek Nayak kprateek.nayak@amd.com
Changes since v4: https://lore.kernel.org/all/20250306055354.52915-1-namjain@linux.microsoft.c... - Rephrased print statement and moved it to sched_domain_debug. (addressing Valentin's comments) Changes since v3: https://lore.kernel.org/all/20250203114738.3109-1-namjain@linux.microsoft.co... - Minor typo correction in comment - Added Tested-by tag from Prateek for x86 Changes since v2: https://lore.kernel.org/all/1731922777-7121-1-git-send-email-ssengar@linux.m... - Use sched_debug() instead of using sched_debug_verbose variable directly (addressing Prateek's comment)
Changes since v1: https://lore.kernel.org/all/1729619853-2597-1-git-send-email-ssengar@linux.m... - Use kernel cmdline param instead of compile time flag.
Adding a link to the other patch which is under review. https://lore.kernel.org/lkml/20241031200431.182443-1-steve.wahl@hpe.com/ Above patch tries to optimize the topology sanity check, whereas this patch makes it optional. We believe both patches can coexist, as even with optimization, there will still be some performance overhead for this check.
kernel/sched/topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index c49aea8c1025..d7254c47af45 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -132,8 +132,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0;
- if (!sched_debug_verbose)
- if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",__func__); return;- }
Nit: I've been told not to break warnings over multiple lines so they can be grep'ed, but given this has the "sched_domain_debug:" prefix I think we could get away with the below.
Regardless: Reviewed-by: Valentin Schneider vschneid@redhat.com
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d7254c47af455..b4dc7c7d2c41c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -133,7 +133,8 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) int level = 0; if (!sched_debug_verbose) {
pr_info_once("%s: Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it\n",
pr_info_once("%s: Scheduler topology debugging disabled, ""add 'sched_verbose' to the cmdline to enable it\n", __func__); return;Hi Valentin, Splitting the warning to different lines give checkpatch error with --strict option. --fix option suggests we keep it like we have it originally(single line). Please let me know if you feel we can change it to something else or if you are fine with picking the change for next iteration. Thanks again.
Hah, didn't know that was in checkpatch :-) As I said before that really was more of a nitpick, consider me OK with the current patch.
Hello maintainers, Since merge window is currently open, I would like to request you to consider picking this change for the next release. Please ignore my email if you have already picked it or planning to do it.
Regards, Naman
linux-stable-mirror@lists.linaro.org
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Naman Jain -
Valentin Schneider