From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757948AbeAHW4o (ORCPT + 1 other); Mon, 8 Jan 2018 17:56:44 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:34170 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756825AbeAHW4m (ORCPT ); Mon, 8 Jan 2018 17:56:42 -0500 X-Google-Smtp-Source: ACJfBota4ZSlVKF/ca5OM0ML0qGAupeEBoK31L0e2oM05kUAK/W2NJwayIfkwFCAql7oePVD1USE0w== From: Rasmus Villemoes To: Matthew Wilcox , Andrew Morton Cc: Eric Biggers , Rasmus Villemoes , linux-kernel@vger.kernel.org Subject: [PATCH] ida: do zeroing in ida_pre_get Date: Mon, 8 Jan 2018 23:56:34 +0100 Message-Id: <20180108225634.15340-1-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.15.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: As far as I can tell, the only place the per-cpu ida_bitmap is populated is in ida_pre_get. The pre-allocated element is stolen in two places in ida_get_new_above, in both cases immediately followed by a memset(0). Since ida_get_new_above is called with locks held, do the zeroing in ida_pre_get, or rather let kmalloc() do it. Also, apparently gcc generates ~44 bytes of code to do a memset(, 0, 128): $ scripts/bloat-o-meter vmlinux.{0,1} add/remove: 0/0 grow/shrink: 2/1 up/down: 5/-88 (-83) Function old new delta ida_pre_get 115 119 +4 vermagic 27 28 +1 ida_get_new_above 715 627 -88 Signed-off-by: Rasmus Villemoes --- lib/idr.c | 2 -- lib/radix-tree.c | 2 +- 2 files changed, 1 insertion(+), 3 deletions(-) diff --git a/lib/idr.c b/lib/idr.c index 2593ce513a18..37c552395b3a 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -300,7 +300,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id) bitmap = this_cpu_xchg(ida_bitmap, NULL); if (!bitmap) return -EAGAIN; - memset(bitmap, 0, sizeof(*bitmap)); bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT; rcu_assign_pointer(*slot, bitmap); } @@ -333,7 +332,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id) bitmap = this_cpu_xchg(ida_bitmap, NULL); if (!bitmap) return -EAGAIN; - memset(bitmap, 0, sizeof(*bitmap)); __set_bit(bit, bitmap->bitmap); radix_tree_iter_replace(root, &iter, slot, bitmap); } diff --git a/lib/radix-tree.c b/lib/radix-tree.c index c8d55565fafa..553248b64d60 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -2124,7 +2124,7 @@ int ida_pre_get(struct ida *ida, gfp_t gfp) preempt_enable(); if (!this_cpu_read(ida_bitmap)) { - struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp); + struct ida_bitmap *bitmap = kzalloc(sizeof(*bitmap), gfp); if (!bitmap) return 0; if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap)) -- 2.15.1