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Message-Id: <1404251250-22992-19-git-send-email-tst@schoebel-theuer.de>
Date: Tue, 1 Jul 2014 23:46:58 +0200
From: Thomas Schoebel-Theuer <tst@...oebel-theuer.de>
To: linux-kernel@...r.kernel.org
Subject: [PATCH 18/50] mars: add new file drivers/block/mars/lib_limiter.c
Signed-off-by: Thomas Schoebel-Theuer <tst@...oebel-theuer.de>
---
drivers/block/mars/lib_limiter.c | 103 +++++++++++++++++++++++++++++++++++++++
1 file changed, 103 insertions(+)
create mode 100644 drivers/block/mars/lib_limiter.c
diff --git a/drivers/block/mars/lib_limiter.c b/drivers/block/mars/lib_limiter.c
new file mode 100644
index 0000000..e8984b7
--- /dev/null
+++ b/drivers/block/mars/lib_limiter.c
@@ -0,0 +1,103 @@
+/* (c) 2012 Thomas Schoebel-Theuer / 1&1 Internet AG */
+
+#include <linux/brick/lib_limiter.h>
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define LIMITER_TIME_RESOLUTION NSEC_PER_SEC
+
+int xio_limit(struct xio_limiter *lim, int amount)
+{
+ int delay = 0;
+ long long now;
+
+ now = cpu_clock(raw_smp_processor_id());
+
+ /* Compute the maximum delay along the path
+ * down to the root of the hierarchy tree.
+ */
+ while (lim != NULL) {
+ long long window = now - lim->lim_stamp;
+
+ /* Sometimes, raw CPU clocks may do weired things...
+ * Smaller windows in the denominator than 1s could fake unrealistic rates.
+ */
+ if (unlikely(lim->lim_min_window <= 0))
+ lim->lim_min_window = 1000;
+ if (unlikely(lim->lim_max_window <= lim->lim_min_window))
+ lim->lim_max_window = lim->lim_min_window + 8000;
+ if (unlikely(window < (long long)lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000)))
+ window = (long long)lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000);
+
+ /* Only use incremental accumulation at repeated calls, but
+ * never after longer pauses.
+ */
+ if (likely(lim->lim_stamp &&
+ window < (long long)lim->lim_max_window * (LIMITER_TIME_RESOLUTION / 1000))) {
+ long long rate_raw;
+ int rate;
+
+ /* Races are possible, but taken into account.
+ * There is no real harm from rarely lost updates.
+ */
+ if (likely(amount > 0)) {
+ lim->lim_accu += amount;
+ lim->lim_cumul += amount;
+ lim->lim_count++;
+ }
+
+ rate_raw = lim->lim_accu * LIMITER_TIME_RESOLUTION / window;
+ rate = rate_raw;
+ if (unlikely(rate_raw > INT_MAX))
+ rate = INT_MAX;
+ lim->lim_rate = rate;
+
+ /* limit exceeded? */
+ if (lim->lim_max_rate > 0 && rate > lim->lim_max_rate) {
+ int this_delay = (window * rate / lim->lim_max_rate - window) / (LIMITER_TIME_RESOLUTION / 1000);
+
+ /* compute maximum */
+ if (this_delay > delay && this_delay > 0)
+ delay = this_delay;
+ }
+
+ /* Try to keep the next window below min_window
+ */
+ window -= lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000);
+ if (window > 0) {
+ long long used_up = (long long)lim->lim_rate * window / LIMITER_TIME_RESOLUTION;
+
+ if (used_up > 0) {
+ lim->lim_stamp += window;
+ lim->lim_accu -= used_up;
+ if (unlikely(lim->lim_accu < 0))
+ lim->lim_accu = 0;
+ }
+ }
+ } else { /* reset, start over with new measurement cycle */
+ if (unlikely(amount < 0))
+ amount = 0;
+ lim->lim_accu = amount;
+ lim->lim_stamp = now - lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000);
+ lim->lim_rate = 0;
+ }
+ lim = lim->lim_father;
+ }
+ return delay;
+}
+EXPORT_SYMBOL_GPL(xio_limit);
+
+void xio_limit_sleep(struct xio_limiter *lim, int amount)
+{
+ int sleep = xio_limit(lim, amount);
+
+ if (sleep > 0) {
+ if (unlikely(lim->lim_max_delay <= 0))
+ lim->lim_max_delay = 1000;
+ if (sleep > lim->lim_max_delay)
+ sleep = lim->lim_max_delay;
+ brick_msleep(sleep);
+ }
+}
+EXPORT_SYMBOL_GPL(xio_limit_sleep);
--
2.0.0
--
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