LinuxPPC-Dev Archive on lore.kernel.org
 help / color / Atom feed
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Lynch <nathanl@linux.ibm.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Mingming Cao <mingming.cao@ibm.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v2 8/9] powerpc/pseries: Protect against hogging the cpu while setting up the stats
Date: Fri, 14 Jun 2019 21:14:06 +0530
Message-ID: <5ae62e552d81305afccd87cf9a56e8ce94e82840.1560526066.git.naveen.n.rao@linux.vnet.ibm.com> (raw)
In-Reply-To: <cover.1560526066.git.naveen.n.rao@linux.vnet.ibm.com>

When enabling or disabling the vcpu dispatch statistics, we do a lot of
work including allocating/deallocating memory across all possible cpus
for the DTL buffer. In order to guard against hogging the cpu for too
long, track the time we're taking and yield the processor if necessary.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/plpar_wrappers.h |  2 +-
 arch/powerpc/platforms/pseries/lpar.c     | 29 ++++++++++++++++-------
 arch/powerpc/platforms/pseries/setup.c    |  2 +-
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/plpar_wrappers.h b/arch/powerpc/include/asm/plpar_wrappers.h
index 5f72f1fa4f81..5e5faabd7ba2 100644
--- a/arch/powerpc/include/asm/plpar_wrappers.h
+++ b/arch/powerpc/include/asm/plpar_wrappers.h
@@ -110,7 +110,7 @@ static inline long register_dtl(unsigned long cpu, unsigned long vpa)
 extern bool register_dtl_buffer_access(bool global);
 extern void unregister_dtl_buffer_access(bool global);
 extern void register_dtl_buffer(int cpu);
-extern void alloc_dtl_buffers(void);
+extern void alloc_dtl_buffers(unsigned long *time_limit);
 extern void vpa_init(int cpu);
 
 static inline long plpar_pte_enter(unsigned long flags,
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 200a96c8626a..318b08ada086 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -62,7 +62,7 @@ static u8 dtl_mask = DTL_LOG_PREEMPT;
 static u8 dtl_mask;
 #endif
 
-void alloc_dtl_buffers(void)
+void alloc_dtl_buffers(unsigned long *time_limit)
 {
 	int cpu;
 	struct paca_struct *pp;
@@ -86,6 +86,11 @@ void alloc_dtl_buffers(void)
 		pp->dispatch_log = dtl;
 		pp->dispatch_log_end = dtl + N_DISPATCH_LOG;
 		pp->dtl_curr = dtl;
+
+		if (time_limit && time_after(jiffies, *time_limit)) {
+			cond_resched();
+			*time_limit = jiffies + HZ;
+		}
 	}
 }
 
@@ -157,7 +162,7 @@ static int vcpudispatch_stats_freq = 50;
 static __be32 *vcpu_associativity, *pcpu_associativity;
 
 
-static void free_dtl_buffers(void)
+static void free_dtl_buffers(unsigned long *time_limit)
 {
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
 	int cpu;
@@ -172,6 +177,11 @@ static void free_dtl_buffers(void)
 		pp->dispatch_log = 0;
 		pp->dispatch_log_end = 0;
 		pp->dtl_curr = 0;
+
+		if (time_limit && time_after(jiffies, *time_limit)) {
+			cond_resched();
+			*time_limit = jiffies + HZ;
+		}
 	}
 #endif
 }
@@ -464,7 +474,7 @@ static void reset_global_dtl_mask(void)
 		lppaca_of(cpu).dtl_enable_mask = dtl_mask;
 }
 
-static int dtl_worker_enable(void)
+static int dtl_worker_enable(unsigned long *time_limit)
 {
 	int rc = 0, state;
 
@@ -483,13 +493,13 @@ static int dtl_worker_enable(void)
 	set_global_dtl_mask(DTL_LOG_ALL);
 
 	/* Setup dtl buffers and register those */
-	alloc_dtl_buffers();
+	alloc_dtl_buffers(time_limit);
 
 	state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/dtl:online",
 					dtl_worker_online, dtl_worker_offline);
 	if (state < 0) {
 		pr_err("vcpudispatch_stats: unable to setup workqueue for DTL processing\n");
-		free_dtl_buffers();
+		free_dtl_buffers(time_limit);
 		reset_global_dtl_mask();
 		unregister_dtl_buffer_access(1);
 		rc = -EINVAL;
@@ -503,14 +513,14 @@ static int dtl_worker_enable(void)
 	return rc;
 }
 
-static void dtl_worker_disable(void)
+static void dtl_worker_disable(unsigned long *time_limit)
 {
 	mutex_lock(&dtl_worker_mutex);
 	dtl_worker_refctr--;
 	if (!dtl_worker_refctr) {
 		cpuhp_remove_state(dtl_worker_state);
 		dtl_worker_state = 0;
-		free_dtl_buffers();
+		free_dtl_buffers(time_limit);
 		reset_global_dtl_mask();
 		unregister_dtl_buffer_access(1);
 	}
@@ -520,6 +530,7 @@ static void dtl_worker_disable(void)
 static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,
 		size_t count, loff_t *ppos)
 {
+	unsigned long time_limit = jiffies + HZ;
 	struct vcpu_dispatch_data *disp;
 	int rc, cmd, cpu;
 	char buf[16];
@@ -552,13 +563,13 @@ static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,
 			disp->last_disp_cpu = -1;
 		}
 
-		rc = dtl_worker_enable();
+		rc = dtl_worker_enable(&time_limit);
 		if (rc) {
 			destroy_cpu_associativity();
 			return rc;
 		}
 	} else {
-		dtl_worker_disable();
+		dtl_worker_disable(&time_limit);
 		destroy_cpu_associativity();
 	}
 
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index e4d75b958593..76fd6de90581 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -279,7 +279,7 @@ static int alloc_dispatch_logs(void)
 	if (!dtl_cache)
 		return 0;
 
-	alloc_dtl_buffers();
+	alloc_dtl_buffers(0);
 
 	/* Register the DTL for the current (boot) cpu */
 	register_dtl_buffer(smp_processor_id());
-- 
2.21.0


  parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 15:43 [PATCH v2 0/9] Provide vcpu dispatch statistics Naveen N. Rao
2019-06-14 15:43 ` [PATCH v2 1/9] powerpc/pseries: Use macros for referring to the DTL enable mask Naveen N. Rao
2019-06-14 15:44 ` [PATCH v2 2/9] powerpc/pseries: Do not save the previous DTL mask value Naveen N. Rao
2019-06-14 15:44 ` [PATCH v2 3/9] powerpc/pseries: Factor out DTL buffer allocation and registration routines Naveen N. Rao
2019-06-14 15:44 ` [PATCH v2 4/9] powerpc/pseries: Introduce helpers to gatekeep DTLB usage Naveen N. Rao
2019-06-14 15:44 ` [PATCH v2 5/9] powerpc/pseries: Generalize hcall_vphn() Naveen N. Rao
2019-06-14 15:44 ` [PATCH v2 6/9] powerpc/pseries: Move mm/book3s64/vphn.c under platforms/pseries/ Naveen N. Rao
2019-06-14 15:44 ` [PATCH v2 7/9] powerpc/pseries: Provide vcpu dispatch statistics Naveen N. Rao
2019-06-14 15:44 ` Naveen N. Rao [this message]
2019-06-14 15:44 ` [PATCH v2 9/9] powerpc/pseries: Add documentation for vcpudispatch_stats Naveen N. Rao

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5ae62e552d81305afccd87cf9a56e8ce94e82840.1560526066.git.naveen.n.rao@linux.vnet.ibm.com \
    --to=naveen.n.rao@linux.vnet.ibm.com \
    --cc=aneesh.kumar@linux.ibm.com \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mingming.cao@ibm.com \
    --cc=mpe@ellerman.id.au \
    --cc=nathanl@linux.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LinuxPPC-Dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linuxppc-dev/0 linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ https://lore.kernel.org/linuxppc-dev \
		linuxppc-dev@lists.ozlabs.org linuxppc-dev@ozlabs.org linuxppc-dev@archiver.kernel.org
	public-inbox-index linuxppc-dev


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linuxppc-dev


AGPL code for this site: git clone https://public-inbox.org/ public-inbox