From: Michal Hocko <mhocko@kernel.org> To: Vlastimil Babka <vbabka@suse.cz> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com Subject: Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable() Date: Tue, 11 Jul 2017 09:16:12 +0200 [thread overview] Message-ID: <20170711071612.GG24852@dhcp22.suse.cz> (raw) In-Reply-To: <337a8a4c-1f27-7371-409d-6a9f181b3871@suse.cz> On Tue 11-07-17 08:56:04, Vlastimil Babka wrote: > On 07/11/2017 08:50 AM, Michal Hocko wrote: > > On Tue 11-07-17 08:26:40, Vlastimil Babka wrote: > >> On 07/11/2017 08:03 AM, Michal Hocko wrote: > >>> > >>> Are you telling me that two if conditions cause more than a second > >>> difference? That sounds suspicious. > >> > >> It's removing also a call to get_unmapped_area(), AFAICS. That means a > >> vma search? > > > > Ohh, right. I have somehow missed that. Is this removal intentional? > > I think it is: "Checking for availability of virtual address range at > the end of the VMA for the incremental size is also reduntant at this > point." I though this referred to this check if (vma->vm_next && vma->vm_next->vm_start < end) becuase get_unampped_area with MAP_FIXED doesn't really check anything. It will simply return the given address. Btw. this also rules out find_vma. > > The > > changelog is silent about it. > > It doesn't explain why it's redundant, indeed. Unfortunately, the commit > f106af4e90ea ("fix checks for expand-in-place mremap") which added this, > also doesn't explain why it's needed. Because it doesn't do anything AFAICS. -- Michal Hocko SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: Vlastimil Babka <vbabka@suse.cz> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com Subject: Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable() Date: Tue, 11 Jul 2017 09:16:12 +0200 [thread overview] Message-ID: <20170711071612.GG24852@dhcp22.suse.cz> (raw) In-Reply-To: <337a8a4c-1f27-7371-409d-6a9f181b3871@suse.cz> On Tue 11-07-17 08:56:04, Vlastimil Babka wrote: > On 07/11/2017 08:50 AM, Michal Hocko wrote: > > On Tue 11-07-17 08:26:40, Vlastimil Babka wrote: > >> On 07/11/2017 08:03 AM, Michal Hocko wrote: > >>> > >>> Are you telling me that two if conditions cause more than a second > >>> difference? That sounds suspicious. > >> > >> It's removing also a call to get_unmapped_area(), AFAICS. That means a > >> vma search? > > > > Ohh, right. I have somehow missed that. Is this removal intentional? > > I think it is: "Checking for availability of virtual address range at > the end of the VMA for the incremental size is also reduntant at this > point." I though this referred to this check if (vma->vm_next && vma->vm_next->vm_start < end) becuase get_unampped_area with MAP_FIXED doesn't really check anything. It will simply return the given address. Btw. this also rules out find_vma. > > The > > changelog is silent about it. > > It doesn't explain why it's redundant, indeed. Unfortunately, the commit > f106af4e90ea ("fix checks for expand-in-place mremap") which added this, > also doesn't explain why it's needed. Because it doesn't do anything AFAICS. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-11 7:16 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-07-10 11:10 [RFC] mm/mremap: Remove redundant checks inside vma_expandable() Anshuman Khandual 2017-07-10 11:10 ` Anshuman Khandual 2017-07-10 13:49 ` Michal Hocko 2017-07-10 13:49 ` Michal Hocko 2017-07-11 4:28 ` Anshuman Khandual 2017-07-11 4:28 ` Anshuman Khandual 2017-07-11 6:03 ` Michal Hocko 2017-07-11 6:03 ` Michal Hocko 2017-07-11 6:26 ` Vlastimil Babka 2017-07-11 6:26 ` Vlastimil Babka 2017-07-11 6:50 ` Michal Hocko 2017-07-11 6:50 ` Michal Hocko 2017-07-11 6:56 ` Vlastimil Babka 2017-07-11 6:56 ` Vlastimil Babka 2017-07-11 7:16 ` Michal Hocko [this message] 2017-07-11 7:16 ` Michal Hocko 2017-07-11 7:22 ` Michal Hocko 2017-07-11 7:22 ` Michal Hocko 2017-07-11 11:19 ` Anshuman Khandual 2017-07-11 11:19 ` Anshuman Khandual 2017-07-11 11:11 ` Anshuman Khandual 2017-07-11 11:11 ` Anshuman Khandual 2017-07-11 11:08 ` Anshuman Khandual 2017-07-11 11:08 ` Anshuman Khandual 2017-07-11 11:22 ` Michal Hocko 2017-07-11 11:22 ` Michal Hocko 2017-07-19 6:49 ` Anshuman Khandual 2017-07-19 6:49 ` Anshuman Khandual 2017-07-11 11:06 ` Anshuman Khandual 2017-07-11 11:06 ` Anshuman Khandual 2017-07-11 9:44 ` Anshuman Khandual 2017-07-11 9:44 ` Anshuman Khandual 2017-07-11 4:29 ` Anshuman Khandual 2017-07-11 4:29 ` Anshuman Khandual
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20170711071612.GG24852@dhcp22.suse.cz \ --to=mhocko@kernel.org \ --cc=akpm@linux-foundation.org \ --cc=khandual@linux.vnet.ibm.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=mike.kravetz@oracle.com \ --cc=vbabka@suse.cz \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.