56 lines
1.9 KiB
Diff
56 lines
1.9 KiB
Diff
From 0f8de4902fe3f3512ee5043c5277d002a488a804 Mon Sep 17 00:00:00 2001
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From: Michael Trapp <michael.trapp@sap.com>
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Date: Thu, 10 Mar 2022 13:18:52 +0100
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Subject: [PATCH] libuuid: extend cache in uuid_generate_time_generic()
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Improve throughput and reduce clock sequence increments
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for high load situation with time based version 1 uuids.
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In a high load scenario, where an application continiously reads time
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based version 1 uuids from uuidd, we have noticed the following
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behaviour.
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The application reads more uuids as there are available in the
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corresponding timeframe and each bulk request results in an increment of
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the clock sequence because of the 'step back' in time. Due to the
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14bit size of the clock sequence this also results in overflows of
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the clock sequence.
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As uuidd calls
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uuid_generate_time_safe()
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uuid_generate_time_generic()
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the default value for the bulk request in the '#ifdef HAVE_TLS' section
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of uuid_generate_time_generic() is set to 1000.
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Extending the 'cache' of uuid_generate_time_generic() by increasing
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the default of num to 1000000 doesn't solve the issue, but reduces
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the clock sequence increments by factor 1000 and it also improves
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the uuid throughput in our setup by factor 3-4.
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It might be possible to implement a cache for
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UUIDD_OP_BULK_TIME_UUID
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UUIDD_OP_TIME_UUID
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in the uuidd request handling, but it would not be as simple as this fix
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in uuid_generate_time_generic().
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Signed-off-by: Karel Zak <kzak@redhat.com>
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---
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libuuid/src/gen_uuid.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/libuuid/src/gen_uuid.c b/libuuid/src/gen_uuid.c
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index d353fa1a0..76d5371ea 100644
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--- a/libuuid/src/gen_uuid.c
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+++ b/libuuid/src/gen_uuid.c
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@@ -453,7 +453,7 @@ static int uuid_generate_time_generic(uuid_t out) {
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num = 0;
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}
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if (num <= 0) {
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- num = 1000;
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+ num = 1000000;
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if (get_uuid_via_daemon(UUIDD_OP_BULK_TIME_UUID,
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out, &num) == 0) {
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last_time = time(NULL);
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--
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2.35.1
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