122 lines
4.3 KiB
Diff
122 lines
4.3 KiB
Diff
From 7c7557d9954eb7d8fa6249af316879dada22829d Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Sat, 11 Jun 2022 12:34:02 +0100
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Subject: [PATCH] rate: Allow burstiness to be controlled
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Previously it was fixed at 2.0 seconds. Allowing it to be adjusted
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upwards could help with large, lumpy requests.
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(cherry picked from commit f79e951c20510381d5cd83c203c670874a4978f4)
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---
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filters/rate/nbdkit-rate-filter.pod | 12 ++++++++++--
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filters/rate/rate.c | 20 +++++++++++++-------
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tests/test-rate.sh | 2 +-
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3 files changed, 24 insertions(+), 10 deletions(-)
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diff --git a/filters/rate/nbdkit-rate-filter.pod b/filters/rate/nbdkit-rate-filter.pod
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index 8956e641..09ce7dbc 100644
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--- a/filters/rate/nbdkit-rate-filter.pod
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+++ b/filters/rate/nbdkit-rate-filter.pod
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@@ -9,6 +9,7 @@ nbdkit-rate-filter - limit bandwidth by connection or server
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[connection-rate=BITSPERSEC]
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[rate-file=FILENAME]
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[connection-rate-file=FILENAME]
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+ [burstiness=SECS]
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=head1 DESCRIPTION
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@@ -63,6 +64,13 @@ Limit total bandwidth across all connections to C<BITSPERSEC>.
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Adjust the per-connection or total bandwidth dynamically by writing
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C<BITSPERSEC> into C<FILENAME>. See L</DYNAMIC ADJUSTMENT> below.
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+=item B<burstiness=>SECS
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+
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+Control the bucket capacity, expressed as a length of time in
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+"rate-equivalent seconds" that the client is allowed to burst for
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+after a period of inactivity. The default is 2.0 seconds. It's not
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+recommended to set this smaller than the default.
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+
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=back
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C<BITSPERSEC> can be specified as a simple number, or you can use a
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@@ -105,8 +113,8 @@ If the size of requests made by your client is much larger than the
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rate limit then you can see long, lumpy sleeps in this filter. In the
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future we may modify the filter to break up large requests
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automatically in order to limit the length of sleeps. Placing the
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-L<nbdkit-blocksize-filter(1)> in front of this filter may help in the
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-meantime.
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+L<nbdkit-blocksize-filter(1)> in front of this filter, or adjusting
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+C<burstiness> upwards may help.
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=head1 FILES
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diff --git a/filters/rate/rate.c b/filters/rate/rate.c
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index 1a70d212..26082f8c 100644
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--- a/filters/rate/rate.c
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+++ b/filters/rate/rate.c
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@@ -68,10 +68,9 @@ static char *rate_file = NULL;
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/* Bucket capacity controls the burst rate. It is expressed as the
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* length of time in "rate-equivalent seconds" that the client can
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- * burst for after a period of inactivity. This could be adjustable
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- * in future.
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+ * burst for after a period of inactivity.
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*/
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-#define BUCKET_CAPACITY 2.0
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+static double bucket_capacity = 2.0 /* seconds */;
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/* Global read and write buckets. */
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static struct bucket read_bucket;
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@@ -142,6 +141,13 @@ rate_config (nbdkit_next_config *next, nbdkit_backend *nxdata,
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return -1;
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return 0;
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}
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+ else if (strcmp (key, "burstiness") == 0) {
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+ if (sscanf (value, "%lg", &bucket_capacity) != 1) {
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+ nbdkit_error ("burstiness must be a floating point number (seconds)");
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+ return -1;
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+ }
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+ return 0;
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+ }
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else
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return next (nxdata, key, value);
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}
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@@ -150,8 +156,8 @@ static int
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rate_get_ready (int thread_model)
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{
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/* Initialize the global buckets. */
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- bucket_init (&read_bucket, rate, BUCKET_CAPACITY);
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- bucket_init (&write_bucket, rate, BUCKET_CAPACITY);
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+ bucket_init (&read_bucket, rate, bucket_capacity);
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+ bucket_init (&write_bucket, rate, bucket_capacity);
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return 0;
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}
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@@ -178,8 +184,8 @@ rate_open (nbdkit_next_open *next, nbdkit_context *nxdata,
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return NULL;
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}
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- bucket_init (&h->read_bucket, connection_rate, BUCKET_CAPACITY);
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- bucket_init (&h->write_bucket, connection_rate, BUCKET_CAPACITY);
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+ bucket_init (&h->read_bucket, connection_rate, bucket_capacity);
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+ bucket_init (&h->write_bucket, connection_rate, bucket_capacity);
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pthread_mutex_init (&h->read_bucket_lock, NULL);
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pthread_mutex_init (&h->write_bucket_lock, NULL);
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diff --git a/tests/test-rate.sh b/tests/test-rate.sh
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index 7305c928..ff781c21 100755
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--- a/tests/test-rate.sh
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+++ b/tests/test-rate.sh
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@@ -56,7 +56,7 @@ nbdkit -U - \
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--filter=blocksize --filter=rate \
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pattern 25M \
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maxdata=65536 \
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- rate=10M \
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+ rate=10M burstiness=2.0 \
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--run 'nbdcopy "$uri" rate.img'
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end_t=$SECONDS
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--
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2.31.1
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