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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AAA3C433EF for ; Wed, 12 Jan 2022 14:56:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DA6AC6B0174; Wed, 12 Jan 2022 09:56:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D556B6B0175; Wed, 12 Jan 2022 09:56:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BA86D6B0176; Wed, 12 Jan 2022 09:56:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0215.hostedemail.com [216.40.44.215]) by kanga.kvack.org (Postfix) with ESMTP id 8A9FC6B0174 for ; Wed, 12 Jan 2022 09:56:02 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1FDBC8249980 for ; Wed, 12 Jan 2022 14:56:02 +0000 (UTC) X-FDA: 79021934964.09.176318C Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf31.hostedemail.com (Postfix) with ESMTP id 871AA20016 for ; Wed, 12 Jan 2022 14:56:01 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id EDE722113A; Wed, 12 Jan 2022 14:55:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1641999359; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5KSUB5kk6nqxyfWFyV07yS90dxBEdeusq9/dOu6x3jE=; b=l/xiyL8QrWWgcg71BMnXFzBYFg1IlHLPgU1TngGuuVcjuCRidcqSKgkdiURr9OCmM/S8Mz yW5vpZpRGS3452NJlNPMWOtgLO1gB9/bZY02dquRSlN+ZaESF51baJKn5t8e7S62jnpUPP 7Ugi2zWPLYCm7N4nK9ghIxWuHZnGqQQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1641999359; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5KSUB5kk6nqxyfWFyV07yS90dxBEdeusq9/dOu6x3jE=; b=DXlVaQErcO2qUlP5shtCFtZwdL197gN301t5uJHizZrhYjsqtdJy4MqtyK1PCrTjSjjnOh Iw+DKH6oq3uAHgAg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 9EAC613B70; Wed, 12 Jan 2022 14:55:59 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 8YT5Jf/r3mF7DwAAMHmgww (envelope-from ); Wed, 12 Jan 2022 14:55:59 +0000 Message-ID: <7bd61a52-57ef-04e4-6298-039308bb8f86@suse.cz> Date: Wed, 12 Jan 2022 15:55:59 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Content-Language: en-US To: Liam Howlett , "maple-tree@lists.infradead.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton Cc: Song Liu , Davidlohr Bueso , "Paul E . McKenney" , Matthew Wilcox , Laurent Dufour , David Rientjes , Axel Rasmussen , Suren Baghdasaryan , Rik van Riel , Peter Zijlstra , Michel Lespinasse , Jerome Glisse , Minchan Kim , Joel Fernandes , Rom Lemarchand References: <20211201142918.921493-1-Liam.Howlett@oracle.com> <20211201142918.921493-18-Liam.Howlett@oracle.com> From: Vlastimil Babka Subject: Re: [PATCH v4 17/66] mmap: Change zeroing of maple tree in __vma_adjust In-Reply-To: <20211201142918.921493-18-Liam.Howlett@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 871AA20016 X-Stat-Signature: txp4r5wufaxw159ew757qbar3usysoi7 Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="l/xiyL8Q"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=DXlVaQEr; dmarc=none; spf=pass (imf31.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Rspamd-Server: rspam03 X-HE-Tag: 1641999361-487895 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/1/21 15:29, Liam Howlett wrote: > Only write to the maple tree if we are not inserting or the insert isn't > going to overwrite the area to clear. This avoids spanning writes and > node coealescing when unnecessary. > > Signed-off-by: Liam R. Howlett > --- > mm/mmap.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 93ed19b2c6ce..c5f92666d145 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -615,6 +615,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, > bool vma_changed = false; > long adjust_next = 0; > int remove_next = 0; > + unsigned long old_start; > > if (next && !insert) { > struct vm_area_struct *exporter = NULL, *importer = NULL; > @@ -740,25 +741,29 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, > vma_interval_tree_remove(next, root); > } > > + old_start = vma->vm_start; > if (start != vma->vm_start) { > - if (vma->vm_start < start) > - vma_mt_szero(mm, vma->vm_start, start); > - else > - vma_changed = true; > + vma_changed = true; This says vma_changed = true even if vma is shrinking, so below we might do an unnecessary vma_store(), no? > vma->vm_start = start; > } > if (end != vma->vm_end) { > - if (vma->vm_end > end) > - vma_mt_szero(mm, end, vma->vm_end); > - else > + if (vma->vm_end > end) { In contrast to the above, here vma_changed is only set when expanding ('vma_expand' would be a more descriptive name maybe?). So why are the two cases handled differently, am I missing something? > + if (!insert || (insert && (insert->vm_start != end))) Note: thanks to lazy evaluation, "insert &&" should be unnecessary? More importantly: is "insert->vm_start == end" a guarantee that insert covers the whole interval from end to vma->vm_end? Probably yes, but a VM_WARN_ON would be in order? > + vma_mt_szero(mm, end, vma->vm_end); I guess it can't happen that insert would cover a later part of this interval, so we could zero only between end vna insert->vm_start? > + } else > vma_changed = true; Same nit about { } block as previously. > vma->vm_end = end; > if (!next) > mm->highest_vm_end = vm_end_gap(vma); > } > > - if (vma_changed) > + if (vma_changed) { > vma_store(mm, vma); > + if (old_start < start) { > + if (insert && (insert->vm_start != old_start)) > + vma_mt_szero(mm, old_start, start); This condition looks actively wrong, no zeroing at all if insert is NULL? > + } > + } > > vma->vm_pgoff = pgoff; > if (adjust_next) {