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62 lines
2.5 KiB
62 lines
2.5 KiB
From 0aa65dc3acba481f7064df936ab49e3bceb1d5bd Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Wed, 20 Mar 2024 14:12:32 -0400
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Subject: [PATCH 2/2] coroutine: reserve 5,000 mappings
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 234: coroutine: cap per-thread local pool size
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RH-Jira: RHEL-28947
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
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RH-Commit: [2/2] 78560c2b947471111cc16c313d6f38db42860a1c (stefanha/centos-stream-qemu-kvm)
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Daniel P. Berrangé <berrange@redhat.com> pointed out that the coroutine
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pool size heuristic is very conservative. Instead of halving
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max_map_count, he suggested reserving 5,000 mappings for non-coroutine
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users based on observations of guests he has access to.
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Fixes: 86a637e48104 ("coroutine: cap per-thread local pool size")
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
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Message-id: 20240320181232.1464819-1-stefanha@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 9352f80cd926fe2dde7c89b93ee33bb0356ff40e)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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util/qemu-coroutine.c | 15 ++++++++++-----
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1 file changed, 10 insertions(+), 5 deletions(-)
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diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c
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index 2790959eaf..eb4eebefdf 100644
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--- a/util/qemu-coroutine.c
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+++ b/util/qemu-coroutine.c
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@@ -377,12 +377,17 @@ static unsigned int get_global_pool_hard_max_size(void)
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NULL) &&
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qemu_strtoi(contents, NULL, 10, &max_map_count) == 0) {
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/*
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- * This is a conservative upper bound that avoids exceeding
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- * max_map_count. Leave half for non-coroutine users like library
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- * dependencies, vhost-user, etc. Each coroutine takes up 2 VMAs so
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- * halve the amount again.
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+ * This is an upper bound that avoids exceeding max_map_count. Leave a
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+ * fixed amount for non-coroutine users like library dependencies,
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+ * vhost-user, etc. Each coroutine takes up 2 VMAs so halve the
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+ * remaining amount.
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*/
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- return max_map_count / 4;
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+ if (max_map_count > 5000) {
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+ return (max_map_count - 5000) / 2;
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+ } else {
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+ /* Disable the global pool but threads still have local pools */
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+ return 0;
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+ }
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}
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#endif
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--
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2.39.3
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