{"id":2175490,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2175490/?format=json","project":{"id":41,"url":"http://patchwork.ozlabs.org/api/1.0/projects/41/?format=json","name":"GNU C Library","link_name":"glibc","list_id":"libc-alpha.sourceware.org","list_email":"libc-alpha@sourceware.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<22984336264c0cb2bad3c2459631ac14d4a890ac.1766051058.git.fweimer@redhat.com>","date":"2025-12-18T10:17:52","name":"[2/3] malloc: Only fill half of the tcache during batch allocation","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"41f4563beb42a866cf360de8f8b2d596fa825c85","submitter":{"id":14312,"url":"http://patchwork.ozlabs.org/api/1.0/people/14312/?format=json","name":"Florian Weimer","email":"fweimer@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/glibc/patch/22984336264c0cb2bad3c2459631ac14d4a890ac.1766051058.git.fweimer@redhat.com/mbox/","series":[{"id":485815,"url":"http://patchwork.ozlabs.org/api/1.0/series/485815/?format=json","date":"2025-12-18T10:17:02","name":"malloc: batched frees","version":1,"mbox":"http://patchwork.ozlabs.org/series/485815/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2175490/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=bvYa+Bul;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=38.145.34.32; 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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1766053078;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:mime-version:mime-version:content-type:content-type:\n in-reply-to:in-reply-to:references:references;\n bh=8QaJkGFaQhr+gicLSON/F0BqcIL5HHIdj/oqO+VKk9g=;\n b=bvYa+BulGHWLqboOPYAbeK+8RKdWLznKmn7CBWRqWSaJ30S9EA4tUaybGq4VMO7i5Y7Z4R\n s2vSu4l7Xos4haLdoTpPaopFQoy0L/+OOJ4Hc7Bc4LWRFEnfyjppveOJK5pV9ckn+dMKI7\n bgJY1vJN8XRMPhbcyCSIlLw/K9yvd20=","X-MC-Unique":"sw9u239PMHqXlP_LQimw0Q-1","X-Mimecast-MFC-AGG-ID":"sw9u239PMHqXlP_LQimw0Q_1766053076","From":"Florian Weimer ","To":"libc-alpha@sourceware.org","Subject":"[PATCH 2/3] malloc: Only fill half of the tcache during batch\n allocation","In-Reply-To":"","Message-ID":"\n <22984336264c0cb2bad3c2459631ac14d4a890ac.1766051058.git.fweimer@redhat.com>","References":"","X-From-Line":"22984336264c0cb2bad3c2459631ac14d4a890ac Mon Sep 17 00:00:00 2001","Date":"Thu, 18 Dec 2025 11:17:52 +0100","User-Agent":"Gnus/5.13 (Gnus v5.13)","MIME-Version":"1.0","X-Scanned-By":"MIMEDefang 3.0 on 10.30.177.12","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"1l6-RAO_GNsVOQcXNmFKq_blCrC0H_V1sdFH-MHqBE8_1766053076","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain","X-BeenThere":"libc-alpha@sourceware.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Libc-alpha mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org"},"content":"This leaves room for subsequent frees.\n---\n malloc/malloc.c | 14 ++++++++++----\n 1 file changed, 10 insertions(+), 4 deletions(-)","diff":"diff --git a/malloc/malloc.c b/malloc/malloc.c\nindex d2184c8d7a..d42f0183e3 100644\n--- a/malloc/malloc.c\n+++ b/malloc/malloc.c\n@@ -3940,8 +3940,11 @@ _int_malloc (mstate av, size_t bytes)\n \t if (__glibc_unlikely (tcache_inactive ()))\n \t\ttcache_init (av);\n \n-\t /* While bin not empty and tcache not full, copy chunks over. */\n-\t while (tcache->num_slots[tc_idx] != 0\n+\t /* While bin not empty and tcache not full, copy chunks over.\n+\t\t Only fill half of the tcache, so that subsequent frees\n+\t\t do not immediately flush the tcache. */\n+\t unsigned int tcache_target_count = mp_.tcache_count / 2;\n+\t while (tcache->num_slots[tc_idx] > tcache_target_count\n \t\t && (tc_victim = last (bin)) != bin)\n \t\t{\n \t\t if (tc_victim != NULL)\n@@ -3988,6 +3991,7 @@ _int_malloc (mstate av, size_t bytes)\n if (tc_idx < mp_.tcache_small_bins)\n tcache_nb = nb;\n int return_cached = 0;\n+ unsigned int tcache_target_count = mp_.tcache_count / 2;\n \n tcache_unsorted_count = 0;\n #endif\n@@ -4066,9 +4070,11 @@ _int_malloc (mstate av, size_t bytes)\n \t if (__glibc_unlikely (tcache_inactive ()))\n \t\ttcache_init (av);\n \t /* Fill cache first, return to user only if cache fills.\n-\t\t We may return one of these chunks later. */\n+\t\t We may return one of these chunks later. Only fill\n+\t\t half of tcache, so that subsequent frees do not flush\n+\t\t it immediately. */\n \t if (tcache_nb > 0\n-\t\t && tcache->num_slots[tc_idx] != 0)\n+\t\t && tcache->num_slots[tc_idx] > tcache_target_count)\n \t\t{\n \t\t tcache_put (victim, tc_idx);\n \t\t return_cached = 1;\n","prefixes":["2/3"]}