From mboxrd@z Thu Jan 1 00:00:00 1970
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From: Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: [PATCH 13/18] vinyl: use lower bound percentile estimate for dump bandwidth
Date: Thu, 16 Aug 2018 19:12:07 +0300
Message-Id: <4bbbdd705bb4a39bfbf81744e3d16e90ee1aaf02.1534432819.git.vdavydov.dev@gmail.com>
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To: kostja@tarantool.org
Cc: tarantool-patches@freelists.org
List-ID: <tarantool-patches.dev.tarantool.org>
Use a lower bound estimate in order not to overestimate dump bandwidth.
For example, if an observation of 12 MB/s falls in bucket 10 .. 15, we
should use 10 MB/s to avoid stalls.
---
src/box/vy_quota.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/src/box/vy_quota.c b/src/box/vy_quota.c
index 64c2ca04..620155ab 100644
--- a/src/box/vy_quota.c
+++ b/src/box/vy_quota.c
@@ -196,8 +196,13 @@ vy_quota_dump(struct vy_quota *q, size_t size, double duration)
/* Account dump bandwidth. */
if (duration > 0) {
histogram_collect(q->dump_bw_hist, size / duration);
- q->dump_bw = histogram_percentile(q->dump_bw_hist,
- VY_DUMP_BANDWIDTH_PCT);
+ /*
+ * To avoid unpredictably long stalls, we need to
+ * know the worst (smallest) dump bandwidth so use
+ * a lower-bound percentile estimate.
+ */
+ q->dump_bw = histogram_percentile_lower(q->dump_bw_hist,
+ VY_DUMP_BANDWIDTH_PCT);
}
}
--
2.11.0