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