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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18DE8C433E7 for ; Sat, 17 Oct 2020 23:15:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CEBC621582 for ; Sat, 17 Oct 2020 23:15:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602976503; bh=HUkpvdzjB+x4x/+1k9Huo5DeTDFFtaqoY9K1Kz6WgNA=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=2GOVhnIbdPYYoan3t3eBxYtX+fi0MsJBuraCuxY+jGNLiRPDCs8kDp5+9ZHD3jRUf AfPN9K0F7g/+vr3fvdU6rTPB8b+ZuRld1ZIWGWwFZKXiu8jim9AQJyFQYmZ8D+6zOp JG6Etr1BTWzUkdjtQB9y5F4KYoDaNmOckC207Ee8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439909AbgJQXPD (ORCPT ); Sat, 17 Oct 2020 19:15:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:48782 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439878AbgJQXPC (ORCPT ); Sat, 17 Oct 2020 19:15:02 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9EE0B20E65; Sat, 17 Oct 2020 23:14:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602976500; bh=HUkpvdzjB+x4x/+1k9Huo5DeTDFFtaqoY9K1Kz6WgNA=; h=Date:From:To:Subject:In-Reply-To:From; b=mINCk+po3lvOicNQVI2g/y1TADHGdefGvE+THjFaET2dER4+fiLoy95PuhWLdN2Cp Fu9La4nU2tj4+vhEMBdCpNDvnnQKDwUPRZoHl2N3F5/gWLWhiz0KitO9xozekay9Hk ZGc4pilw8Qo3GEBZWz33q12GfAebpFdtDIXnbkVk= Date: Sat, 17 Oct 2020 16:14:59 -0700 From: Andrew Morton To: akpm@linux-foundation.org, alexander.h.duyck@linux.intel.com, axboe@kernel.dk, bgeffon@google.com, christian.brauner@ubuntu.com, christian@brauner.io, dancol@google.com, fw@deneb.enyo.de, hannes@cmpxchg.org, jannh@google.com, joaodias@google.com, joel@joelfernandes.org, ktkhai@virtuozzo.com, linux-man@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, minchan@kernel.org, mm-commits@vger.kernel.org, oleksandr@redhat.com, rientjes@google.com, sfr@canb.auug.org.au, shakeelb@google.com, sj38.park@gmail.com, sjpark@amazon.de, sonnyrao@google.com, sspatil@google.com, surenb@google.com, timmurray@google.com, torvalds@linux-foundation.org, vbabka@suse.cz, yuehaibing@huawei.com Subject: [patch 26/40] mm/madvise: introduce process_madvise() syscall: an external memory hinting API Message-ID: <20201017231459.Lp8onBbxK%akpm@linux-foundation.org> In-Reply-To: <20201017161314.88890b87fae7446ccc13c902@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Minchan Kim Subject: mm/madvise: introduce process_madvise() syscall: an external memory hinting API There is usecase that System Management Software(SMS) want to give a memory hint like MADV_[COLD|PAGEEOUT] to other processes and in the case of Android, it is the ActivityManagerService. The information required to make the reclaim decision is not known to the app. Instead, it is known to the centralized userspace daemon(ActivityManagerService), and that daemon must be able to initiate reclaim on its own without any app involvement. To solve the issue, this patch introduces a new syscall process_madvise(2). It uses pidfd of an external process to give the hint. It also supports vector address range because Android app has thousands of vmas due to zygote so it's totally waste of CPU and power if we should call the syscall one by one for each vma.(With testing 2000-vma syscall vs 1-vector syscall, it showed 15% performance improvement. I think it would be bigger in real practice because the testing ran very cache friendly environment). Another potential use case for the vector range is to amortize the cost ofTLB shootdowns for multiple ranges when using MADV_DONTNEED; this could benefit users like TCP receive zerocopy and malloc implementations. In future, we could find more usecases for other advises so let's make it happens as API since we introduce a new syscall at this moment. With that, existing madvise(2) user could replace it with process_madvise(2) with their own pid if they want to have batch address ranges support feature. ince it could affect other process's address range, only privileged process(PTRACE_MODE_ATTACH_FSCREDS) or something else(e.g., being the same UID) gives it the right to ptrace the process could use it successfully. The flag argument is reserved for future use if we need to extend the API. I think supporting all hints madvise has/will supported/support to process_madvise is rather risky. Because we are not sure all hints make sense from external process and implementation for the hint may rely on the caller being in the current context so it could be error-prone. Thus, I just limited hints as MADV_[COLD|PAGEOUT] in this patch. If someone want to add other hints, we could hear the usecase and review it for each hint. It's safer for maintenance rather than introducing a buggy syscall but hard to fix it later. So finally, the API is as follows, ssize_t process_madvise(int pidfd, const struct iovec *iovec, unsigned long vlen, int advice, unsigned int flags); DESCRIPTION The process_madvise() system call is used to give advice or directions to the kernel about the address ranges from external process as well as local process. It provides the advice to address ranges of process described by iovec and vlen. The goal of such advice is to improve system or application performance. The pidfd selects the process referred to by the PID file descriptor specified in pidfd. (See pidofd_open(2) for further information) The pointer iovec points to an array of iovec structures, defined in as: struct iovec { void *iov_base; /* starting address */ size_t iov_len; /* number of bytes to be advised */ }; The iovec describes address ranges beginning at address(iov_base) and with size length of bytes(iov_len). The vlen represents the number of elements in iovec. The advice is indicated in the advice argument, which is one of the following at this moment if the target process specified by pidfd is external. MADV_COLD MADV_PAGEOUT Permission to provide a hint to external process is governed by a ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2). The process_madvise supports every advice madvise(2) has if target process is in same thread group with calling process so user could use process_madvise(2) to extend existing madvise(2) to support vector address ranges. RETURN VALUE On success, process_madvise() returns the number of bytes advised. This return value may be less than the total number of requested bytes, if an error occurred. The caller should check return value to determine whether a partial advice occurred. FAQ: Q.1 - Why does any external entity have better knowledge? Quote from Sandeep "For Android, every application (including the special SystemServer) are forked from Zygote. The reason of course is to share as many libraries and classes between the two as possible to benefit from the preloading during boot. After applications start, (almost) all of the APIs end up calling into this SystemServer process over IPC (binder) and back to the application. In a fully running system, the SystemServer monitors every single process periodically to calculate their PSS / RSS and also decides which process is "important" to the user for interactivity. So, because of how these processes start _and_ the fact that the SystemServer is looping to monitor each process, it does tend to *know* which address range of the application is not used / useful. Besides, we can never rely on applications to clean things up themselves. We've had the "hey app1, the system is low on memory, please trim your memory usage down" notifications for a long time[1]. They rely on applications honoring the broadcasts and very few do. So, if we want to avoid the inevitable killing of the application and restarting it, some way to be able to tell the OS about unimportant memory in these applications will be useful. - ssp Q.2 - How to guarantee the race(i.e., object validation) between when giving a hint from an external process and get the hint from the target process? process_madvise operates on the target process's address space as it exists at the instant that process_madvise is called. If the space target process can run between the time the process_madvise process inspects the target process address space and the time that process_madvise is actually called, process_madvise may operate on memory regions that the calling process does not expect. It's the responsibility of the process calling process_madvise to close this race condition. For example, the calling process can suspend the target process with ptrace, SIGSTOP, or the freezer cgroup so that it doesn't have an opportunity to change its own address space before process_madvise is called. Another option is to operate on memory regions that the caller knows a priori will be unchanged in the target process. Yet another option is to accept the race for certain process_madvise calls after reasoning that mistargeting will do no harm. The suggested API itself does not provide synchronization. It also apply other APIs like move_pages, process_vm_write. The race isn't really a problem though. Why is it so wrong to require that callers do their own synchronization in some manner? Nobody objects to write(2) merely because it's possible for two processes to open the same file and clobber each other's writes --- instead, we tell people to use flock or something. Think about mmap. It never guarantees newly allocated address space is still valid when the user tries to access it because other threads could unmap the memory right before. That's where we need synchronization by using other API or design from userside. It shouldn't be part of API itself. If someone needs more fine-grained synchronization rather than process level, there were two ideas suggested - cookie[2] and anon-fd[3]. Both are applicable via using last reserved argument of the API but I don't think it's necessary right now since we have already ways to prevent the race so don't want to add additional complexity with more fine-grained optimization model. To make the API extend, it reserved an unsigned long as last argument so we could support it in future if someone really needs it. Q.3 - Why doesn't ptrace work? Injecting an madvise in the target process using ptrace would not work for us because such injected madvise would have to be executed by the target process, which means that process would have to be runnable and that creates the risk of the abovementioned race and hinting a wrong VMA. Furthermore, we want to act the hint in caller's context, not the callee's, because the callee is usually limited in cpuset/cgroups or even freezed state so they can't act by themselves quick enough, which causes more thrashing/kill. It doesn't work if the target process are ptraced(e.g., strace, debugger, minidump) because a process can have at most one ptracer. [1] https://developer.android.com/topic/performance/memory" [2] process_getinfo for getting the cookie which is updated whenever vma of process address layout are changed - Daniel Colascione - https://lore.kernel.org/lkml/20190520035254.57579-1-minchan@kernel.org/T/#m7694416fd179b2066a2c62b5b139b14e3894e224 [3] anonymous fd which is used for the object(i.e., address range) validation - Michal Hocko - https://lore.kernel.org/lkml/20200120112722.GY18451@dhcp22.suse.cz/ [minchan@kernel.org: fix process_madvise build break for arm64] Link: http://lkml.kernel.org/r/20200303145756.GA219683@google.com [minchan@kernel.org: fix build error for mips of process_madvise] Link: http://lkml.kernel.org/r/20200508052517.GA197378@google.com [akpm@linux-foundation.org: fix patch ordering issue] [akpm@linux-foundation.org: fix arm64 whoops] [minchan@kernel.org: make process_madvise() vlen arg have type size_t, per Florian] [akpm@linux-foundation.org: fix i386 build] [sfr@canb.auug.org.au: fix syscall numbering] Link: https://lkml.kernel.org/r/20200905142639.49fc3f1a@canb.auug.org.au [sfr@canb.auug.org.au: madvise.c needs compat.h] Link: https://lkml.kernel.org/r/20200908204547.285646b4@canb.auug.org.au [minchan@kernel.org: fix mips build] Link: https://lkml.kernel.org/r/20200909173655.GC2435453@google.com [yuehaibing@huawei.com: remove duplicate header which is included twice] Link: https://lkml.kernel.org/r/20200915121550.30584-1-yuehaibing@huawei.com [minchan@kernel.org: do not use helper functions for process_madvise] Link: https://lkml.kernel.org/r/20200921175539.GB387368@google.com [akpm@linux-foundation.org: pidfd_get_pid() gained an argument] [sfr@canb.auug.org.au: fix up for "iov_iter: transparently handle compat iovecs in import_iovec"] Link: https://lkml.kernel.org/r/20200928212542.468e1fef@canb.auug.org.au Link: http://lkml.kernel.org/r/20200302193630.68771-3-minchan@kernel.org Link: http://lkml.kernel.org/r/20200508183320.GA125527@google.com Link: http://lkml.kernel.org/r/20200622192900.22757-4-minchan@kernel.org Link: https://lkml.kernel.org/r/20200901000633.1920247-4-minchan@kernel.org Reviewed-by: Suren Baghdasaryan Reviewed-by: Vlastimil Babka Acked-by: David Rientjes Signed-off-by: Minchan Kim Signed-off-by: YueHaibing Signed-off-by: Stephen Rothwell Cc: Alexander Duyck Cc: Brian Geffon Cc: Christian Brauner Cc: Daniel Colascione Cc: Jann Horn Cc: Jens Axboe Cc: Joel Fernandes Cc: Johannes Weiner Cc: John Dias Cc: Kirill Tkhai Cc: Michal Hocko Cc: Oleksandr Natalenko Cc: Sandeep Patil Cc: SeongJae Park Cc: SeongJae Park Cc: Shakeel Butt Cc: Sonny Rao Cc: Tim Murray Cc: Christian Brauner Cc: Florian Weimer Cc: Signed-off-by: Andrew Morton --- arch/alpha/kernel/syscalls/syscall.tbl | 1 arch/arm/tools/syscall.tbl | 1 arch/arm64/include/asm/unistd.h | 2 arch/arm64/include/asm/unistd32.h | 2 arch/ia64/kernel/syscalls/syscall.tbl | 1 arch/m68k/kernel/syscalls/syscall.tbl | 1 arch/microblaze/kernel/syscalls/syscall.tbl | 1 arch/mips/kernel/syscalls/syscall_n32.tbl | 1 arch/mips/kernel/syscalls/syscall_n64.tbl | 1 arch/mips/kernel/syscalls/syscall_o32.tbl | 1 arch/parisc/kernel/syscalls/syscall.tbl | 1 arch/powerpc/kernel/syscalls/syscall.tbl | 1 arch/s390/kernel/syscalls/syscall.tbl | 1 arch/sh/kernel/syscalls/syscall.tbl | 1 arch/sparc/kernel/syscalls/syscall.tbl | 1 arch/x86/entry/syscalls/syscall_32.tbl | 1 arch/x86/entry/syscalls/syscall_64.tbl | 1 arch/xtensa/kernel/syscalls/syscall.tbl | 1 include/linux/syscalls.h | 2 include/uapi/asm-generic/unistd.h | 4 kernel/sys_ni.c | 1 mm/madvise.c | 93 +++++++++++++++++- 22 files changed, 117 insertions(+), 3 deletions(-) --- a/arch/alpha/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/alpha/kernel/syscalls/syscall.tbl @@ -479,3 +479,4 @@ 547 common openat2 sys_openat2 548 common pidfd_getfd sys_pidfd_getfd 549 common faccessat2 sys_faccessat2 +550 common process_madvise sys_process_madvise --- a/arch/arm64/include/asm/unistd32.h~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/arm64/include/asm/unistd32.h @@ -887,6 +887,8 @@ __SYSCALL(__NR_openat2, sys_openat2) __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd) #define __NR_faccessat2 439 __SYSCALL(__NR_faccessat2, sys_faccessat2) +#define __NR_process_madvise 440 +__SYSCALL(__NR_process_madvise, sys_process_madvise) /* * Please add new compat syscalls above this comment and update --- a/arch/arm64/include/asm/unistd.h~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/arm64/include/asm/unistd.h @@ -38,7 +38,7 @@ #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) -#define __NR_compat_syscalls 440 +#define __NR_compat_syscalls 441 #endif #define __ARCH_WANT_SYS_CLONE --- a/arch/arm/tools/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/arm/tools/syscall.tbl @@ -453,3 +453,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/ia64/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/ia64/kernel/syscalls/syscall.tbl @@ -360,3 +360,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/m68k/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/m68k/kernel/syscalls/syscall.tbl @@ -439,3 +439,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/microblaze/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/microblaze/kernel/syscalls/syscall.tbl @@ -445,3 +445,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/mips/kernel/syscalls/syscall_n32.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/mips/kernel/syscalls/syscall_n32.tbl @@ -378,3 +378,4 @@ 437 n32 openat2 sys_openat2 438 n32 pidfd_getfd sys_pidfd_getfd 439 n32 faccessat2 sys_faccessat2 +440 n32 process_madvise sys_process_madvise --- a/arch/mips/kernel/syscalls/syscall_n64.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/mips/kernel/syscalls/syscall_n64.tbl @@ -354,3 +354,4 @@ 437 n64 openat2 sys_openat2 438 n64 pidfd_getfd sys_pidfd_getfd 439 n64 faccessat2 sys_faccessat2 +440 n64 process_madvise sys_process_madvise --- a/arch/mips/kernel/syscalls/syscall_o32.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/mips/kernel/syscalls/syscall_o32.tbl @@ -427,3 +427,4 @@ 437 o32 openat2 sys_openat2 438 o32 pidfd_getfd sys_pidfd_getfd 439 o32 faccessat2 sys_faccessat2 +440 o32 process_madvise sys_process_madvise --- a/arch/parisc/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/parisc/kernel/syscalls/syscall.tbl @@ -437,3 +437,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/powerpc/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/powerpc/kernel/syscalls/syscall.tbl @@ -529,3 +529,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/s390/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/s390/kernel/syscalls/syscall.tbl @@ -442,3 +442,4 @@ 437 common openat2 sys_openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise sys_process_madvise --- a/arch/sh/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/sh/kernel/syscalls/syscall.tbl @@ -442,3 +442,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/sparc/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/sparc/kernel/syscalls/syscall.tbl @@ -485,3 +485,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/arch/x86/entry/syscalls/syscall_32.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/x86/entry/syscalls/syscall_32.tbl @@ -444,3 +444,4 @@ 437 i386 openat2 sys_openat2 438 i386 pidfd_getfd sys_pidfd_getfd 439 i386 faccessat2 sys_faccessat2 +440 i386 process_madvise sys_process_madvise --- a/arch/x86/entry/syscalls/syscall_64.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/x86/entry/syscalls/syscall_64.tbl @@ -361,6 +361,7 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise # # x32-specific system call numbers start at 512 to avoid cache impact --- a/arch/xtensa/kernel/syscalls/syscall.tbl~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/arch/xtensa/kernel/syscalls/syscall.tbl @@ -410,3 +410,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common process_madvise sys_process_madvise --- a/include/linux/syscalls.h~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/include/linux/syscalls.h @@ -879,6 +879,8 @@ asmlinkage long sys_munlockall(void); asmlinkage long sys_mincore(unsigned long start, size_t len, unsigned char __user * vec); asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior); +asmlinkage long sys_process_madvise(int pidfd, const struct iovec __user *vec, + size_t vlen, int behavior, unsigned int flags); asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, unsigned long prot, unsigned long pgoff, unsigned long flags); --- a/include/uapi/asm-generic/unistd.h~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/include/uapi/asm-generic/unistd.h @@ -857,9 +857,11 @@ __SYSCALL(__NR_openat2, sys_openat2) __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd) #define __NR_faccessat2 439 __SYSCALL(__NR_faccessat2, sys_faccessat2) +#define __NR_process_madvise 440 +__SYSCALL(__NR_process_madvise, sys_process_madvise) #undef __NR_syscalls -#define __NR_syscalls 440 +#define __NR_syscalls 441 /* * 32 bit systems traditionally used different --- a/kernel/sys_ni.c~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/kernel/sys_ni.c @@ -280,6 +280,7 @@ COND_SYSCALL(mlockall); COND_SYSCALL(munlockall); COND_SYSCALL(mincore); COND_SYSCALL(madvise); +COND_SYSCALL(process_madvise); COND_SYSCALL(remap_file_pages); COND_SYSCALL(mbind); COND_SYSCALL_COMPAT(mbind); --- a/mm/madvise.c~mm-madvise-introduce-process_madvise-syscall-an-external-memory-hinting-api +++ a/mm/madvise.c @@ -17,6 +17,8 @@ #include #include #include +#include +#include #include #include #include @@ -27,7 +29,6 @@ #include #include #include -#include #include @@ -988,6 +989,18 @@ madvise_behavior_valid(int behavior) } } +static bool +process_madvise_behavior_valid(int behavior) +{ + switch (behavior) { + case MADV_COLD: + case MADV_PAGEOUT: + return true; + default: + return false; + } +} + /* * The madvise(2) system call. * @@ -1035,6 +1048,11 @@ madvise_behavior_valid(int behavior) * MADV_DONTDUMP - the application wants to prevent pages in the given range * from being included in its core dump. * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump. + * MADV_COLD - the application is not expected to use this memory soon, + * deactivate pages in this range so that they can be reclaimed + * easily if memory pressure hanppens. + * MADV_PAGEOUT - the application is not expected to use this memory soon, + * page out the pages in this range immediately. * * return values: * zero - success @@ -1151,3 +1169,76 @@ SYSCALL_DEFINE3(madvise, unsigned long, { return do_madvise(current->mm, start, len_in, behavior); } + +SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, + size_t, vlen, int, behavior, unsigned int, flags) +{ + ssize_t ret; + struct iovec iovstack[UIO_FASTIOV], iovec; + struct iovec *iov = iovstack; + struct iov_iter iter; + struct pid *pid; + struct task_struct *task; + struct mm_struct *mm; + size_t total_len; + unsigned int f_flags; + + if (flags != 0) { + ret = -EINVAL; + goto out; + } + + ret = import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter); + if (ret < 0) + goto out; + + pid = pidfd_get_pid(pidfd, &f_flags); + if (IS_ERR(pid)) { + ret = PTR_ERR(pid); + goto free_iov; + } + + task = get_pid_task(pid, PIDTYPE_PID); + if (!task) { + ret = -ESRCH; + goto put_pid; + } + + if (task->mm != current->mm && + !process_madvise_behavior_valid(behavior)) { + ret = -EINVAL; + goto release_task; + } + + mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS); + if (IS_ERR_OR_NULL(mm)) { + ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; + goto release_task; + } + + total_len = iov_iter_count(&iter); + + while (iov_iter_count(&iter)) { + iovec = iov_iter_iovec(&iter); + ret = do_madvise(mm, (unsigned long)iovec.iov_base, + iovec.iov_len, behavior); + if (ret < 0) + break; + iov_iter_advance(&iter, iovec.iov_len); + } + + if (ret == 0) + ret = total_len - iov_iter_count(&iter); + + mmput(mm); + return ret; + +release_task: + put_task_struct(task); +put_pid: + put_pid(pid); +free_iov: + kfree(iov); +out: + return ret; +} _