From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7771BC433FE for ; Tue, 18 Oct 2022 20:50:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229635AbiJRUuQ (ORCPT ); Tue, 18 Oct 2022 16:50:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230046AbiJRUuN (ORCPT ); Tue, 18 Oct 2022 16:50:13 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CEE539BB5 for ; Tue, 18 Oct 2022 13:50:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 00593616F1 for ; Tue, 18 Oct 2022 20:50:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52F6CC433C1; Tue, 18 Oct 2022 20:50:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666126205; bh=0JtWsc3oSV6j+nAEMWxIX+hEcA5B+8ds7h6plbh1hQ8=; h=Date:To:From:Subject:From; b=i7MfycE1kI/uDeRF6PTZ6PxIem+ek368+5gKWQp7y1p1uqKkHI9j49Hd1Z8TX9d4k GMdiOKPweUM3NOom85a6xzgESWi4A/49b4Xs2ZPIpNPZCHcs7tzg3St4smw8THj5ny wvvTPXf4atMMxi8HyvPINz0rfe7waCTL1VCuBygA= Date: Tue, 18 Oct 2022 13:50:04 -0700 To: mm-commits@vger.kernel.org, senozhatsky@chromium.org, ngupta@vflare.org, minchan@kernel.org, ubizjak@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: + zram-use-try_cmpxchg-in-update_used_max.patch added to mm-unstable branch Message-Id: <20221018205005.52F6CC433C1@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: zram: use try_cmpxchg in update_used_max has been added to the -mm mm-unstable branch. Its filename is zram-use-try_cmpxchg-in-update_used_max.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-use-try_cmpxchg-in-update_used_max.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Uros Bizjak Subject: zram: use try_cmpxchg in update_used_max Date: Tue, 18 Oct 2022 16:51:54 +0200 Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in update_used_max. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, reorder code a bit to remove additional compare and conditional jump from the assembly code. Together, hese two changes save 15 bytes from the function when compiled for x86_64. No functional change intended. Link: https://lkml.kernel.org/r/20221018145154.3699-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak Cc: Minchan Kim Cc: Nitin Gupta Cc: Sergey Senozhatsky Signed-off-by: Andrew Morton --- drivers/block/zram/zram_drv.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) --- a/drivers/block/zram/zram_drv.c~zram-use-try_cmpxchg-in-update_used_max +++ a/drivers/block/zram/zram_drv.c @@ -193,16 +193,13 @@ static void update_position(u32 *index, static inline void update_used_max(struct zram *zram, const unsigned long pages) { - unsigned long old_max, cur_max; - - old_max = atomic_long_read(&zram->stats.max_used_pages); + unsigned long cur_max = atomic_long_read(&zram->stats.max_used_pages); do { - cur_max = old_max; - if (pages > cur_max) - old_max = atomic_long_cmpxchg( - &zram->stats.max_used_pages, cur_max, pages); - } while (old_max != cur_max); + if (cur_max >= pages) + return; + } while (!atomic_long_try_cmpxchg(&zram->stats.max_used_pages, + &cur_max, pages)); } static inline void zram_fill_page(void *ptr, unsigned long len, _ Patches currently in -mm which might be from ubizjak@gmail.com are zram-use-try_cmpxchg-in-update_used_max.patch llist-avoid-extra-memory-read-in-llist_add_batch.patch