From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AAC062AD32 for ; Tue, 28 Oct 2025 23:31:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761694266; cv=none; b=WHwoNLQd4Yc2i+nttMkiToFIWOvuNHNFOn+l1qiJxhw/r+QGdLv3GHINkWOVRwnLPTuJp9OE8dZ9ZQlTVar7QwQXuo6vGPGe1Jwntp3ReQjRy9OpYW6J1zETQq0sCQgyi3KtDuWllnXRLhS6fVr7v+MguFW9JRsXjouOmfmfq8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761694266; c=relaxed/simple; bh=qU4S1MyGTpizf+Sqcaay2KvWdHoiqH/2dt7lhd9c3hs=; h=Date:To:From:Subject:Message-Id; b=N2D6P3AyWoi0nJ3uQyrm/Ul2f9VIq2bwEXK640zB6DkSR8Lc4I8i6uHKW3CwcZ9of8PjaO4WLw0DPELEdJ4jsFlUkidrOR8qYlhqQVKsO8GBtB2zh5qfcsCwqSve5DXcizrtTS1GkpiTxaJa12mudc4ro2mejeWM6AlETrw65aU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=LpEbIfT5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="LpEbIfT5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D67EC4CEE7; Tue, 28 Oct 2025 23:31:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1761694266; bh=qU4S1MyGTpizf+Sqcaay2KvWdHoiqH/2dt7lhd9c3hs=; h=Date:To:From:Subject:From; b=LpEbIfT5ccTIHgLCzdJqzFud4FCCawHrv0nopVygJtmiN1Ac1/g6d6lknUBATMqDF BUZ8e0Zvi7dEhl/2txdfuG+tzua3V6GbeUMQX2U/hZGlK3u196HduR2uw82kcxYlXa 4Z6QtSm13zTSQBRL+WlW/Y1tkuBoq2nyVK9lIfKs= Date: Tue, 28 Oct 2025 16:31:05 -0700 To: mm-commits@vger.kernel.org,shikemeng@huaweicloud.com,nphamcs@gmail.com,kasong@tencent.com,chrisl@kernel.org,baohua@kernel.org,bhe@redhat.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-swap-select-swap-device-with-default-priority-round-robin.patch added to mm-new branch Message-Id: <20251028233106.2D67EC4CEE7@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/swap: select swap device with default priority round robin has been added to the -mm mm-new branch. Its filename is mm-swap-select-swap-device-with-default-priority-round-robin.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-select-swap-device-with-default-priority-round-robin.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. 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: Baoquan He Subject: mm/swap: select swap device with default priority round robin Date: Tue, 28 Oct 2025 11:43:08 +0800 Swap devices are assumed to have similar accessing speed when swapon if no priority is specified. It's unfair and doesn't make sense just because one swap device is swapped on firstly, its priority will be higher than the one swapped on later. Here, set all swap devicess to have priority '-1' by default. With this change, swap device with default priority will be selected round robin when swapping out. This can improve the swapping efficiency a lot among multiple swap devices with default priority. Below are swapon output during the processes when high pressure vm-scability test is being taken: 1) This is pre-commit a2468cc9bfdf, swap device is selectd one by one by priority from high to low when one swap device is exhausted: ------------------------------------ [root@hp-dl385g10-03 ~]# swapon NAME TYPE SIZE USED PRIO /dev/zram0 partition 16G 16G -1 /dev/zram1 partition 16G 966.2M -2 /dev/zram2 partition 16G 0B -3 /dev/zram3 partition 16G 0B -4 2) This is behaviour with commit a2468cc9bfdf, on node, swap device sharing the same node id is selected firstly until exhausted; while on node no swap device sharing the node id it selects the one with highest priority until exhaustd: ------------------------------------ [root@hp-dl385g10-03 ~]# swapon NAME TYPE SIZE USED PRIO /dev/zram0 partition 16G 15.7G -2 /dev/zram1 partition 16G 3.4G -3 /dev/zram2 partition 16G 3.4G -4 /dev/zram3 partition 16G 2.6G -5 3) After this patch applied, swap devices with default priority are selectd round robin: ------------------------------------ [root@hp-dl385g10-03 block]# swapon NAME TYPE SIZE USED PRIO /dev/zram0 partition 16G 6.6G -1 /dev/zram1 partition 16G 6.6G -1 /dev/zram2 partition 16G 6.6G -1 /dev/zram3 partition 16G 6.6G -1 With the change, about 18% efficiency promotion relative to node based way as below. (Surely, the pre-commit a2468cc9bfdf way is the worst.) vm-scability test: ================== Test with: usemem --init-time -O -y -x -n 31 2G (4G memcg, zram as swap) one by one: node based: round robin: System time: 1087.38 s 637.92 s 526.74 s (lower is better) Sum Throughput: 2036.55 MB/s 3546.56 MB/s 4207.56 MB/s (higher is better) Single process Throughput: 65.69 MB/s 114.40 MB/s 135.72 MB/s (high is better) free latency: 15769409.48 us 10138455.99 us 6810119.01 us(lower is better) Link: https://lkml.kernel.org/r/20251028034308.929550-3-bhe@redhat.com Signed-off-by: Baoquan He Suggested-by: Chris Li Acked-by: Chris Li Acked-by: Nhat Pham Cc: Barry Song Cc: Kairui Song Cc: Kemeng Shi Signed-off-by: Andrew Morton --- mm/swapfile.c | 30 ++++-------------------------- 1 file changed, 4 insertions(+), 26 deletions(-) --- a/mm/swapfile.c~mm-swap-select-swap-device-with-default-priority-round-robin +++ a/mm/swapfile.c @@ -74,7 +74,7 @@ atomic_long_t nr_swap_pages; EXPORT_SYMBOL_GPL(nr_swap_pages); /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */ long total_swap_pages; -static int least_priority; +#define DEF_SWAP_PRIO -1 unsigned long swapfile_maximum_size; #ifdef CONFIG_MIGRATION bool swap_migration_ad_supported; @@ -2707,10 +2707,7 @@ static void setup_swap_info(struct swap_ struct swap_cluster_info *cluster_info, unsigned long *zeromap) { - if (prio >= 0) - si->prio = prio; - else - si->prio = --least_priority; + si->prio = prio; /* * the plist prio is negated because plist ordering is * low-to-high, while swap ordering is high-to-low @@ -2728,16 +2725,7 @@ static void _enable_swap_info(struct swa total_swap_pages += si->pages; assert_spin_locked(&swap_lock); - /* - * both lists are plists, and thus priority ordered. - * swap_active_head needs to be priority ordered for swapoff(), - * which on removal of any swap_info_struct with an auto-assigned - * (i.e. negative) priority increments the auto-assigned priority - * of any lower-priority swap_info_structs. - * swap_avail_head needs to be priority ordered for folio_alloc_swap(), - * which allocates swap pages from the highest available priority - * swap_info_struct. - */ + plist_add(&si->list, &swap_active_head); /* Add back to available list */ @@ -2887,16 +2875,6 @@ SYSCALL_DEFINE1(swapoff, const char __us } spin_lock(&p->lock); del_from_avail_list(p, true); - if (p->prio < 0) { - struct swap_info_struct *si = p; - - plist_for_each_entry_continue(si, &swap_active_head, list) { - si->prio++; - si->list.prio--; - si->avail_list.prio--; - } - least_priority++; - } plist_del(&p->list, &swap_active_head); atomic_long_sub(p->pages, &nr_swap_pages); total_swap_pages -= p->pages; @@ -3607,7 +3585,7 @@ SYSCALL_DEFINE2(swapon, const char __use } mutex_lock(&swapon_mutex); - prio = -1; + prio = DEF_SWAP_PRIO; if (swap_flags & SWAP_FLAG_PREFER) prio = swap_flags & SWAP_FLAG_PRIO_MASK; enable_swap_info(si, prio, swap_map, cluster_info, zeromap); _ Patches currently in -mm which might be from bhe@redhat.com are mm-swap-do-not-choose-swap-device-according-to-numa-node.patch mm-swap-select-swap-device-with-default-priority-round-robin.patch