From nobody Sat Nov 30 05:44:27 2024 Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) (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 31E5B64A8F for ; Wed, 11 Sep 2024 17:38:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726076309; cv=none; b=acPHkk0lu/66ZvHTX2vCaZyuNT7vGRfzXPtuBlx5QUfqJTobiZGER9ijeE2UqKugFVjyU7SjScB6R3pTNHKX3d4zAtoSkapH9jXU7lvibTgyfdRoz8M3OUFZbmmMn4gjEswzNhmDtoZ593J/onxis2XKRtinwNfoDmeWkNCvdeI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726076309; c=relaxed/simple; bh=qtxnw7qh+1XsyvwzmeOIvcx5EHBYVBzoCXfIw3qb1I4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BBmHc9hMSBf+XKIdb2T5pGos11vjpPhj0IARiK23tWWXCBHEi9jBRpQk9gmmUpK/9HQ8AsOr5hGb3rNeH0uqx1FcLf4GMX3BSKaQgPhZP6x8+Ohr8F8uw4VdtFPa3ms0FMv142EDm6kQOGEWeULOqYYW11J1XZc4NyBe6kl3Wy8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=sKbgIhC5; arc=none smtp.client-ip=91.218.175.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="sKbgIhC5" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1726076305; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zdRYrmHTTIwJmPoGD8yXUb5ju89WcIe4B/6wB3n+klc=; b=sKbgIhC52Z4AaapQANOdJh+4RWQIISni3JuRbutGf66gah7JT7+031Q1R2aM1Bpj+VTBT8 nbwZfHeHH7PbbmBeviTN+5nXKc+CWO+E0zZytvbJFWeDIzwHkPj7y9eEHhRXwNuIkp6kpk m2Fz6RQCzJyk0GVpNWMmMXPusdlaFE8= From: Shakeel Butt To: Andrew Morton Cc: Matthew Wilcox , Johannes Weiner , Omar Sandoval , Chris Mason , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , linux-fsdevel@vger.kernel.org Subject: [PATCH 1/2] mm: optimize truncation of shadow entries Date: Wed, 11 Sep 2024 10:38:00 -0700 Message-ID: <20240911173801.4025422-2-shakeel.butt@linux.dev> In-Reply-To: <20240911173801.4025422-1-shakeel.butt@linux.dev> References: <20240911173801.4025422-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" The kernel truncates the page cache in batches of PAGEVEC_SIZE. For each batch, it traverses the page cache tree and collects the entries (folio and shadow entries) in the struct folio_batch. For the shadow entries present in the folio_batch, it has to traverse the page cache tree for each individual entry to remove them. This patch optimize this by removing them in a single tree traversal. On large machines in our production which run workloads manipulating large amount of data, we have observed that a large amount of CPUs are spent on truncation of very large files (100s of GiBs file sizes). More specifically most of time was spent on shadow entries cleanup, so optimizing the shadow entries cleanup, even a little bit, has good impact. To evaluate the changes, we created 200GiB file on a fuse fs and in a memcg. We created the shadow entries by triggering reclaim through memory.reclaim in that specific memcg and measure the simple truncation operation. # time truncate -s 0 file time (sec) Without 5.164 +- 0.059 With-patch 4.21 +- 0.066 (18.47% decrease) Signed-off-by: Shakeel Butt Acked-by: Johannes Weiner --- mm/truncate.c | 50 +++++++++++++++++++++++--------------------------- 1 file changed, 23 insertions(+), 27 deletions(-) diff --git a/mm/truncate.c b/mm/truncate.c index 0668cd340a46..c7c19c816c2e 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -72,50 +72,46 @@ static void clear_shadow_entries(struct address_space *= mapping, static void truncate_folio_batch_exceptionals(struct address_space *mappin= g, struct folio_batch *fbatch, pgoff_t *indices) { + XA_STATE(xas, &mapping->i_pages, indices[0]); + int nr =3D folio_batch_count(fbatch); + struct folio *folio; int i, j; - bool dax; =20 /* Handled by shmem itself */ if (shmem_mapping(mapping)) return; =20 - for (j =3D 0; j < folio_batch_count(fbatch); j++) + for (j =3D 0; j < nr; j++) if (xa_is_value(fbatch->folios[j])) break; =20 - if (j =3D=3D folio_batch_count(fbatch)) + if (j =3D=3D nr) return; =20 - dax =3D dax_mapping(mapping); - if (!dax) { - spin_lock(&mapping->host->i_lock); - xa_lock_irq(&mapping->i_pages); + if (dax_mapping(mapping)) { + for (i =3D j; i < nr; i++) { + if (xa_is_value(fbatch->folios[i])) + dax_delete_mapping_entry(mapping, indices[i]); + } + goto out; } =20 - for (i =3D j; i < folio_batch_count(fbatch); i++) { - struct folio *folio =3D fbatch->folios[i]; - pgoff_t index =3D indices[i]; - - if (!xa_is_value(folio)) { - fbatch->folios[j++] =3D folio; - continue; - } + xas_set_update(&xas, workingset_update_node); =20 - if (unlikely(dax)) { - dax_delete_mapping_entry(mapping, index); - continue; - } + spin_lock(&mapping->host->i_lock); + xas_lock_irq(&xas); =20 - __clear_shadow_entry(mapping, index, folio); + xas_for_each(&xas, folio, indices[nr-1]) { + if (xa_is_value(folio)) + xas_store(&xas, NULL); } =20 - if (!dax) { - xa_unlock_irq(&mapping->i_pages); - if (mapping_shrinkable(mapping)) - inode_add_lru(mapping->host); - spin_unlock(&mapping->host->i_lock); - } - fbatch->nr =3D j; + xas_unlock_irq(&xas); + if (mapping_shrinkable(mapping)) + inode_add_lru(mapping->host); + spin_unlock(&mapping->host->i_lock); +out: + folio_batch_remove_exceptionals(fbatch); } =20 /** --=20 2.43.5