linux-kernel - [PATCH 3/3] vmevent: Implement cross event type

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 9 Apr 2012 03:38:35 +0400
From:	Anton Vorontsov <anton.vorontsov@...aro.org>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	Leonid Moiseichuk <leonid.moiseichuk@...ia.com>,
	John Stultz <john.stultz@...aro.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: [PATCH 3/3] vmevent: Implement cross event type

This patch implements a new event type, it will trigger whenever a
value crosses a user-specified threshold. It works two-way, i.e. when
a value crosses the threshold from a lesser values side to a greater
values side, and vice versa.

We use the event type in an userspace low-memory killer: we get a
notification when memory becomes low, so we start freeing memory by
killing unneeded processes, and we get notification when memory hits
the threshold from another side, so we know that we freed enough of
memory.

Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
---
 include/linux/vmevent.h              |    9 +++++++++
 mm/vmevent.c                         |   21 +++++++++++++++++++++
 tools/testing/vmevent/vmevent-test.c |   15 ++++++++++-----
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/include/linux/vmevent.h b/include/linux/vmevent.h
index 64357e4..00cc04f 100644
--- a/include/linux/vmevent.h
+++ b/include/linux/vmevent.h
@@ -22,6 +22,15 @@ enum {
 	 * Sample value is less than user-specified value
 	 */
 	VMEVENT_ATTR_STATE_VALUE_LT	= (1UL << 0),
+	/*
+	 * Sample value crossed user-specified value
+	 */
+	VMEVENT_ATTR_STATE_VALUE_CROSS	= (1UL << 2),
+
+	/* Last saved state, used internally by the kernel. */
+	__VMEVENT_ATTR_STATE_LAST	= (1UL << 30),
+	/* Not first sample, used internally by the kernel. */
+	__VMEVENT_ATTR_STATE_NFIRST	= (1UL << 31),
 };
 
 struct vmevent_attr {
diff --git a/mm/vmevent.c b/mm/vmevent.c
index a56174f..f8fd2d6 100644
--- a/mm/vmevent.c
+++ b/mm/vmevent.c
@@ -1,5 +1,6 @@
 #include <linux/anon_inodes.h>
 #include <linux/atomic.h>
+#include <linux/compiler.h>
 #include <linux/vmevent.h>
 #include <linux/syscalls.h>
 #include <linux/timer.h>
@@ -94,6 +95,26 @@ static bool vmevent_match(struct vmevent_watch *watch)
 		if (attr->state & VMEVENT_ATTR_STATE_VALUE_LT) {
 			if (value < attr->value)
 				return true;
+		} else if (attr->state & VMEVENT_ATTR_STATE_VALUE_CROSS) {
+			bool fst = !(attr->state & __VMEVENT_ATTR_STATE_NFIRST);
+			bool old = attr->state & __VMEVENT_ATTR_STATE_LAST;
+			bool new = value < attr->value;
+			bool chg = old ^ new;
+			bool ret = chg;
+
+			/*
+			 * This is not 'lt' or 'gt' match, so on the first
+			 * sample assume we crossed the threshold.
+			 */
+			if (unlikely(fst)) {
+				attr->state |= __VMEVENT_ATTR_STATE_NFIRST;
+				ret = true;
+			}
+
+			attr->state &= ~__VMEVENT_ATTR_STATE_LAST;
+			attr->state |= new ? __VMEVENT_ATTR_STATE_LAST : 0;
+
+			return ret;
 		}
 	}
 
diff --git a/tools/testing/vmevent/vmevent-test.c b/tools/testing/vmevent/vmevent-test.c
index 534f827..39e93af 100644
--- a/tools/testing/vmevent/vmevent-test.c
+++ b/tools/testing/vmevent/vmevent-test.c
@@ -33,20 +33,25 @@ int main(int argc, char *argv[])
 
 	config = (struct vmevent_config) {
 		.sample_period_ns	= 1000000000L,
-		.counter		= 4,
+		.counter		= 5,
 		.attrs			= {
-			[0]			= {
+			{
+				.type	= VMEVENT_ATTR_NR_FREE_PAGES,
+				.state	= VMEVENT_ATTR_STATE_VALUE_CROSS,
+				.value	= phys_pages / 2,
+			},
+			{
 				.type	= VMEVENT_ATTR_NR_FREE_PAGES,
 				.state	= VMEVENT_ATTR_STATE_VALUE_LT,
 				.value	= phys_pages,
 			},
-			[1]			= {
+			{
 				.type	= VMEVENT_ATTR_NR_AVAIL_PAGES,
 			},
-			[2]			= {
+			{
 				.type	= VMEVENT_ATTR_NR_SWAP_PAGES,
 			},
-			[3]			= {
+			{
 				.type	= 0xffff, /* invalid */
 			},
 		},
-- 
1.7.7.6
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/