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From 8da81d2aba2768ced497790cc05b9f73c6268833 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
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Date: Tue, 22 Jan 2019 17:30:48 +0100
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Subject: [PATCH] journald: periodically drop cache for all dead PIDs
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In normal use, this allow us to drop dead entries from the cache and reduces
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the cache size so that we don't evict entries unnecessarily. The time limit is
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there mostly to serve as a guard against malicious logging from many different
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PIDs.
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(cherry-picked from commit 91714a7f427a6c9c5c3be8b3819fee45050028f3)
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Related: #1664976
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---
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src/journal/journald-context.c | 28 ++++++++++++++++++++++++++--
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src/journal/journald-server.h | 2 ++
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2 files changed, 28 insertions(+), 2 deletions(-)
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diff --git a/src/journal/journald-context.c b/src/journal/journald-context.c
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index 0f0dc1de4..51f79fd80 100644
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--- a/src/journal/journald-context.c
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+++ b/src/journal/journald-context.c
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@@ -541,15 +541,39 @@ refresh:
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}
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static void client_context_try_shrink_to(Server *s, size_t limit) {
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+ ClientContext *c;
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+ usec_t t;
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+
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assert(s);
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+ /* Flush any cache entries for PIDs that have already moved on. Don't do this
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+ * too often, since it's a slow process. */
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+ t = now(CLOCK_MONOTONIC);
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+ if (s->last_cache_pid_flush + MAX_USEC < t) {
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+ unsigned n = prioq_size(s->client_contexts_lru), idx = 0;
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+
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+ /* We do a number of iterations based on the initial size of the prioq. When we remove an
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+ * item, a new item is moved into its places, and items to the right might be reshuffled.
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+ */
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+ for (unsigned i = 0; i < n; i++) {
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+ c = prioq_peek_by_index(s->client_contexts_lru, idx);
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+
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+ assert(c->n_ref == 0);
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+
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+ if (!pid_is_unwaited(c->pid))
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+ client_context_free(s, c);
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+ else
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+ idx ++;
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+ }
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+
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+ s->last_cache_pid_flush = t;
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+ }
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+
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/* Bring the number of cache entries below the indicated limit, so that we can create a new entry without
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* breaching the limit. Note that we only flush out entries that aren't pinned here. This means the number of
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* cache entries may very well grow beyond the limit, if all entries stored remain pinned. */
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while (hashmap_size(s->client_contexts) > limit) {
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- ClientContext *c;
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-
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c = prioq_pop(s->client_contexts_lru);
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if (!c)
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break; /* All remaining entries are pinned, give up */
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diff --git a/src/journal/journald-server.h b/src/journal/journald-server.h
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index 983be8bb8..c6c9b1fb1 100644
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--- a/src/journal/journald-server.h
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+++ b/src/journal/journald-server.h
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@@ -163,6 +163,8 @@ struct Server {
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Hashmap *client_contexts;
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Prioq *client_contexts_lru;
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+ usec_t last_cache_pid_flush;
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+
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ClientContext *my_context; /* the context of journald itself */
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ClientContext *pid1_context; /* the context of PID 1 */
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};
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