From: "Kirill A. Shutemov" <kirill@shutemov.name> To: Johannes Weiner <hannes@cmpxchg.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <peterz@infradead.org> Subject: Re: [PATCH 01/12] uprobes: split THPs before trying replace them Date: Wed, 25 Jan 2017 21:38:39 +0300 [thread overview] Message-ID: <20170125183839.GC4157@node> (raw) In-Reply-To: <20170125183510.GB17286@cmpxchg.org> On Wed, Jan 25, 2017 at 01:35:10PM -0500, Johannes Weiner wrote: > On Wed, Jan 25, 2017 at 08:55:22AM -0800, Srikar Dronamraju wrote: > > > > > > > > > For THPs page_check_address() always fails. It's better to split them > > > > > first before trying to replace. > > > > > > > > So what does this mean. uprobes simply fails to work when trying to > > > > place a probe into a THP memory region? > > > > > > Looks like we can end up with endless retry loop in uprobe_write_opcode(). > > > > > > > How come nobody noticed (and reported) this when using the feature? > > > > > > I guess it's not often used for anon memory. > > > > > > > The first time the breakpoint is hit on a page, it replaces the text > > page with anon page. Now lets assume we insert breakpoints in all the > > pages in a range. Here each page is individually replaced by a non THP > > anonpage. (since we dont have bulk breakpoint insertion support, > > breakpoint insertion happens one at a time). Now the only interesting > > case may be when each of these replaced pages happen to be physically > > contiguous so that THP kicks in to replace all of these pages with one > > THP page. Can happen in practice? > > > > Are there any other cases that I have missed? > > We use a hack in our applications where we open /proc/self/maps, copy > text segments to a staging area, then create overlay anon mappings on > top and copy the text back into them. Now we have THP-backed text and > very little iTLB pressure :-) Just use tmpfs with huge pages :) > That said, we haven't run into the uprobes issue yet. Is it possible to have uprobes in anon memory? -- Kirill A. Shutemov
WARNING: multiple messages have this Message-ID (diff)
From: "Kirill A. Shutemov" <kirill@shutemov.name> To: Johannes Weiner <hannes@cmpxchg.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <peterz@infradead.org> Subject: Re: [PATCH 01/12] uprobes: split THPs before trying replace them Date: Wed, 25 Jan 2017 21:38:39 +0300 [thread overview] Message-ID: <20170125183839.GC4157@node> (raw) In-Reply-To: <20170125183510.GB17286@cmpxchg.org> On Wed, Jan 25, 2017 at 01:35:10PM -0500, Johannes Weiner wrote: > On Wed, Jan 25, 2017 at 08:55:22AM -0800, Srikar Dronamraju wrote: > > > > > > > > > For THPs page_check_address() always fails. It's better to split them > > > > > first before trying to replace. > > > > > > > > So what does this mean. uprobes simply fails to work when trying to > > > > place a probe into a THP memory region? > > > > > > Looks like we can end up with endless retry loop in uprobe_write_opcode(). > > > > > > > How come nobody noticed (and reported) this when using the feature? > > > > > > I guess it's not often used for anon memory. > > > > > > > The first time the breakpoint is hit on a page, it replaces the text > > page with anon page. Now lets assume we insert breakpoints in all the > > pages in a range. Here each page is individually replaced by a non THP > > anonpage. (since we dont have bulk breakpoint insertion support, > > breakpoint insertion happens one at a time). Now the only interesting > > case may be when each of these replaced pages happen to be physically > > contiguous so that THP kicks in to replace all of these pages with one > > THP page. Can happen in practice? > > > > Are there any other cases that I have missed? > > We use a hack in our applications where we open /proc/self/maps, copy > text segments to a staging area, then create overlay anon mappings on > top and copy the text back into them. Now we have THP-backed text and > very little iTLB pressure :-) Just use tmpfs with huge pages :) > That said, we haven't run into the uprobes issue yet. Is it possible to have uprobes in anon memory? -- Kirill A. Shutemov -- 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:[~2017-01-25 18:38 UTC|newest] Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-01-24 16:28 [PATCH 00/12] Fix few rmap-related THP bugs Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 01/12] uprobes: split THPs before trying replace them Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 18:08 ` Rik van Riel 2017-01-24 18:08 ` Rik van Riel 2017-01-24 21:28 ` Andrew Morton 2017-01-24 21:28 ` Andrew Morton 2017-01-24 22:22 ` Kirill A. Shutemov 2017-01-24 22:22 ` Kirill A. Shutemov 2017-01-24 22:35 ` Andrew Morton 2017-01-24 22:35 ` Andrew Morton 2017-01-24 22:56 ` Kirill A. Shutemov 2017-01-24 22:56 ` Kirill A. Shutemov 2017-01-25 16:55 ` Srikar Dronamraju 2017-01-25 16:55 ` Srikar Dronamraju 2017-01-25 17:44 ` Rik van Riel 2017-01-25 17:44 ` Kirill A. Shutemov 2017-01-25 17:44 ` Kirill A. Shutemov 2017-01-25 18:35 ` Johannes Weiner 2017-01-25 18:35 ` Johannes Weiner 2017-01-25 18:38 ` Kirill A. Shutemov [this message] 2017-01-25 18:38 ` Kirill A. Shutemov 2017-01-26 2:54 ` Srikar Dronamraju 2017-01-26 2:54 ` Srikar Dronamraju 2017-01-25 18:22 ` Johannes Weiner 2017-01-25 18:22 ` Johannes Weiner 2017-01-24 16:28 ` [PATCH 02/12] mm: introduce page_check_walk() Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 21:41 ` Andrew Morton 2017-01-24 21:41 ` Andrew Morton 2017-01-24 22:50 ` Kirill A. Shutemov 2017-01-24 22:50 ` Kirill A. Shutemov 2017-01-24 22:55 ` Andrew Morton 2017-01-24 22:55 ` Andrew Morton 2017-01-25 17:53 ` Kirill A. Shutemov 2017-01-25 17:53 ` Kirill A. Shutemov 2017-01-25 1:19 ` kbuild test robot 2017-01-25 1:19 ` kbuild test robot 2017-01-25 1:59 ` kbuild test robot 2017-01-25 1:59 ` kbuild test robot 2017-01-24 16:28 ` [PATCH 03/12] mm: fix handling PTE-mapped THPs in page_referenced() Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 04/12] mm: fix handling PTE-mapped THPs in page_idle_clear_pte_refs() Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 05/12] mm, rmap: check all VMAs that PTE-mapped THP can be part of Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 06/12] mm: convert page_mkclean_one() to page_check_walk() Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-25 1:44 ` kbuild test robot 2017-01-25 1:44 ` kbuild test robot 2017-01-25 2:00 ` kbuild test robot 2017-01-25 2:00 ` kbuild test robot 2017-01-24 16:28 ` [PATCH 07/12] mm: convert try_to_unmap_one() " Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-25 3:13 ` kbuild test robot 2017-01-25 3:13 ` kbuild test robot 2017-01-24 16:28 ` [PATCH 08/12] mm, ksm: convert write_protect_page() " Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 09/12] mm, uprobes: convert __replace_page() " Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-26 2:58 ` Srikar Dronamraju 2017-01-26 2:58 ` Srikar Dronamraju 2017-01-24 16:28 ` [PATCH 10/12] mm: convert page_mapped_in_vma() " Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 11/12] mm: drop page_check_address{,_transhuge} Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-24 16:28 ` [PATCH 12/12] mm: convert remove_migration_pte() to page_check_walk() Kirill A. Shutemov 2017-01-24 16:28 ` Kirill A. Shutemov 2017-01-25 1:54 ` kbuild test robot 2017-01-25 1:54 ` kbuild test robot
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